What was the most significant event on April 21 during the U.S. Civil War?

My response:
Pictures
1. Map of Grierson's raid and Streight's raid;
2. Ranger Bloody Bill Anderson;
3. John S. Mosby;
4. Jessie James was a confederate partisan along with his brother Frank James and Cole Younger

1861: Wars and rumors of wars. Within 2 weeks of secession the citizens of Richmond and I expect many other cities and towns expected an assault to come any day. At this time war was romanticized. Soon it would be all too real to many especially on the borders of Union and Confederacy in Northern VA; the Shenandoah. Tennessee and Missouri.
1862: CSA congress passes the Partisan Act – names like Bloody Bill Anderson in Missouri; John S. Mosby in Virginia, William Clarke Quantrill in Kansas and Missouri, Cole Younger and Frank & Jesse James were Confederate partisans
1863: Western theater union cavalry raids continue (COL Griersons) and begin (COL Streight’s). Grierson’s raid would ultimately succeed while Sleight’s raid would fail when the entire command is captured by Nathan Bedford Forrest.

Since RallyPoint truncates survey selection text I am posting events that were not included and then the full text of each survey choice below:
A. Sunday, April 21, 1861: The "Pawnee War" It was rumored that the gunboat Pawnee was coming up James River, with the intention of capturing or bombarding the city of Richmond. Passing Rocketts, the port of Richmond, we found the citizens assembled there by thousands; old men, boys, women, girls, women with babies in their arms, in fact nearly the whole population. Some had shotguns, some had rifles, some pistols, some swords, some canes, and some had made large piles of stones on the wharves, to use against the enemy. They were all determined that the ship should never get to the wharf. It makes me laugh now, after my experience of war, to think what the citizens were then doing!
The night passed without incident; the expected Pawnee did not come. The next day we returned to Richmond on two barges, that were sent down the river for us. We won a great deal of glory in this campaign, as everyone thought we had done wonders. In marching from Rocketts up Main Street to our quarters, which were between Eighth and Ninth Streets, we had an ovation nearly all the way. Thus closed the "Pawnee War."
B. Monday, April 21, 1862: The Confederate Congress passed the Partisan Ranger Act. This law was written to help recruit irregulars to serve in the Civil War. Many men lived and died as Partisan Rangers.
A few survived and lived normal lives after the war, while others never gave up after the war ended. This is a story about the Partisan Rangers, who were also known as “bushwhackers” and “guerillas”, depending on which side of the battle line you were standing.
One of the most famous Rangers roamed the roads of Ray County and thanks to him, our local history is known worldwide.
On Oct. 26, 1864, a company of Missouri Partisan Rangers led by Capt. William Anderson were camped north of present-day Orrick on land owned by “Riley” Blythe, which was then known as Albany.
C. Tuesday, April 21, 1863: Streight’s Raid begins. Union Colonel Abel Streight begins a raid into northern Alabama and Georgia with the goal of cutting the Western and Atlantic Railroad between Chattanooga, Tennessee and Atlanta. The raid ended when Confederate General Nathan Bedford Forrest captured Streight’s entire command near Rome, Georgia.
The plan called for Streight and General Greenville Dodge to move from central Tennessee into northwestern Alabama. Dodge would lead a diversionary attack on Tuscumbia, Alabama, while Streight would take nearly 2,000 troopers across northern Alabama and into Georgia. Streight outfitted his men with mules instead of horses, as he felt they were better adapted to the rugged terrain of the southern Appalachians. The expedition ran into trouble almost immediately when the mules arrived at Nashville in poor condition. A Confederate cavalry detachment swooped in and caused the mules to stampede, and it took two days to round them up.
The first part of the expedition went well. Dodge captured Tuscumbia, and Streight continued east toward Georgia. But on April 29, Streight’s command was attacked by part of General Nathan Bedford Forrest’s cavalry. Streight’s men set a trap for the pursuing Rebels, and it worked well. The Confederate cavalry detachment, led by Captain William Forrest, brother of Nathan Bedford, found itself under fire from two sides. William Forrest was wounded, and the Federals continued on their mission.
But now General Nathan Bedford Forrest was on Streight’s trail, and he would not let up. The Yankees were in hostile territory, and several times the Rebels received important information from local residents that allowed them to gain the upper hand. Finally, Forrest confronted the exhausted Union troops. Under a flag of truce, they discussed terms of surrender on May 3. Forrest had just 600 men, less than half of what Streight now possessed. But Forrest spread his men around the woods. As he met with Streight, couriers from nonexistent units rode up with reports. Streight took the bait, and agreed to surrender. When the Confederates finally emerged to gather the Yankee’s weaponry, the Union colonel realized that he had been had by the crafty Forrest.
D. Thursday, April 21, 1864: U.S.S. Owasco, Lieutenant Commander Henry, seized blockade running British schooner Laura with cargo of guns in the Gulf of Mexico off Velasco, Texas. Boat expedition under Acting Ensign Christopher Carven, U.S.S. Sagamore, took over 100 bales of cotton and destroyed 300 additional bales near Clay Landing, on the Suwannee River, Florida. Boat expedition commanded by Acting Master John K. Crosby from U.S.S. Cimarron destroyed a rice mill and Thursday, April 21, 1864: 5,000 bushels of rice stored at Winyah Bay, South Carolina. The blockaded South could ill afford to lose such food stuffs.
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
1. Tuesday, April 21, 1863 --- Grierson’s Raid – This afternoon, Hatch’s raiders reach the town of Palo Alto, and find a Confederate force there, the 2nd Tennessee Cavalry, under command of Lt. Col. C.R. Barteau, who drives Hatch back north to Okolona and Tupelo---but the Iowans destroy track as they go. Hatch has drawn away all Southern threat to Grierson’s rear, Grierson, with the two Illinois regiments, dashes southward, captures Starkville and burns a considerable stockpile of Confederate stores there. He detaches a battalion to Bankston, who find a vast store of leather goods---saddles, shoes, and other vital military goods---and destroys that.
http://civilwarsesquicentdaily-wolfshield.blogspot.com/search?q=April+21%2C+1863
2. Tuesday, April 21, 1863 --- Admiral Porter attempts another run past the Vicksburg defenses, and succeeds at bringing over 20 transport vessels through.
http://civilwarsesquicentdaily-wolfshield.blogspot.com/search?q=April+21%2C+1863
3. Tuesday, April 21, 1863 --- Pres. Lincoln signs a proclamation admitting West Virginia as the 35th State in the Union, effective June 20, 1863.
http://civilwarsesquicentdaily-wolfshield.blogspot.com/search?q=April+21%2C+1863
4. Thursday, April 21, 1864: Federal Major General Nathaniel Banks harassed troops were in the process of withdrawing from Grand Ecore to Alexandria, Louisiana, as the Red River Campaign came to a close. Confederate troops pursued Banks with hit-and-run attacks but mounted no offensive.
http://thisweekinthecivilwar.com/?p=1841
5. President Abraham Lincoln conferred with governors from Ohio, Indiana, Illinois and Iowa, and also reviewed seventy-two court-martial cases.
http://thisweekinthecivilwar.com/?p=1841
6. Thursday, April 21, 1864 --- Repairs to the USS Eastport succeed, and the ironclad is raised from the riverbed and put afloat once more.
http://civilwarsesquicentdaily-wolfshield.blogspot.com/search?q=April+21%2C+1864
7. Thursday, April 21, 1864 --- Longstreet’s troops have moved even closer to Lee’s main body of troops, and marches to Gordonsville, Virginia today, lining up on Lee's left flank.
http://civilwarsesquicentdaily-wolfshield.blogspot.com/search?q=April+21%2C+1864
8. Thursday, April 21, 1864 --- Sergeant Alexander Downing, of the 11th Iowa Infantry, is coming to the end of his furlough home. He has helped his father put in a crop of wheat while at home, and records his thoughts in his journal as he begins to travel back to the front: This is a warm, pleasant day and I bade farewell to my home folks and friends and started back to the army, my thirty-day furlough being almost up. I went on horseback, brother John going along as far as Allen’s Grove, to Uncle John Moore’s to remain overnight, while John returned home, taking back the horse which I rode. Though the spring has been very late, the farmers here have all their small grain in and it is starting fine. The country around Allen’s Grove is very nice farming land; it is rolling, with plenty of timber and close to a good market; it is becoming very thickly settled. Scott county, Iowa.
http://civilwarsesquicentdaily-wolfshield.blogspot.com/search?q=April+21%2C+1864
9. Thursday, April 21, 1864: Rear Admiral Lee emphasized the urgent need to destroy C.S.S. Albemarle. If the ram could not be disposed of by ship's gunfire, the Admiral suggested that an attempt be made with tor-pedoes. However, Lee wrote Commander Henry K. Davenport, senior officer in the North Carolina sounds: " I propose that two of our vessels should attack the ram, one on each side at close quarters, and drive her roof in. That railroad iron will not stand the concussion of our heavy guns.
Our vessels must maneuver to avoid being rammed, and once close alongside, there will be no danger of firing into each other. . . . I think the ram must be weak, and must fail if attacked on the side." Lieutenant Commander William T. Truxtun, U.S.S. Tacony, wrote Davenport on the same day: "The ironclad, from all accounts, is very much like the first Merrimack, with a very long and very sharp submerged prow. . . . The loss of so good a vessel as the Southfield and so valuable a life as that of the brave Flusser should show the impossibility of contending successfully with a heavy and powerful ironclad with nothing but one or two very vulnerable wooden vessels."
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
10. Thursday, April 21, 1864: U.S.S. Petrel, Acting Master McElroy, U.S.S. Prairie Bird, Acting Ensign John W. Chambers, and transport Freestone steamed up the Yazoo River to operate with Union troops attacking Yazoo City. Coming abreast the city, Petrel was fired upon by a Confederate battery and sharp shooters. The river was too narrow to come about, so Petrel steamed past the batteries to avoid the direct line of fire. The 170-ton Prairie Bird, however dropped downriver out of range of the bat-teries. McElroy made preparation to join her, but on April 22nd, was again taken under attack by rifle and artillery fire and disabled. McElroy attempted to destroy Petrel to prevent her being taken as a prize, but was captured before he could successfully put his small wooden gunboat to the torch. Reporting the capture, Confederate General Wirt Adams wrote: I removed her fine armament of eight 24-pounder guns and the most valuable stores and had her burned to the water's edge."
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
11. Thursday, April 21, 1864: Boat crews from U.S.S. Howquah, Fort Jackson, and Niphon, commanded by Acting Lieutenant Joseph B. Breck, destroyed Confederate salt works on Masonboro Sound, North Carolina. The sailors landed under cover of darkness at 9 p.m. without being detected and rapidly demolished the works while taking some 160 prisoners. Breck then returned to the ships, which were standing by to cover the operation with gunfire if necessary. Major General W.H.C. Whiting, CSA, noted that the incident demonstrated the necessity of maintaining a guard to protect "these points", and that henceforth there would be no salt works constructed at Masonboro Inlet. The Union Navy conducted a regular campaign against Southern salt works as the need for salt was critical in the Confederacy.
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
12. Thursday, April 21, 1864: Boat crews from U.S.S. Ethan Allan, Acting Master Isaac A. Pennell, landed at Cane Patch, near Murrell's Inlet, South Carolina, and destroyed a salt work which Pennell, who led the expedition himself, described as "much more extensive than I expected After mixing most of the 2,000 bushels of salt into the sand of the beach, the Union sailors fired the four salt works as well as some 30 buildings in the surrounding area. The next day, off Wither's Swash, Pennell sent Acting Master William H. Winslow and Acting Ensign James H. Bunting ashore with two boat crews to destroy a smaller salt work.
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
13. Thursday, April 21, 1864: Rear Admiral Dahlgren wrote Secretary Welles suggesting that since "the demands of the public service elsewhere will prevent the detail of more ironclads for service at Charleston, which will necessarily postpone any serious attack on the interior defenses of the harbor," the combined Army and Navy forces should focus their attention and efforts on occupying Long Island and at-tacking Sullivan's Island. The demands elsewhere to which Dahlgren referred were the preparations for the assault on Mobile Bay by Rear Admiral Farragut.
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
14. Thursday, April 21, 1864: U.S.S. Eureka, Acting Ensign Isaac Hallock, nearing the shore below Urbanna, Virginia, to capture two small boats, 'was taken under heavy fire by concealed Southern soldiers. The 85-foot, 50-ton steamer, though surprised by the attack, replied immediately and forced the Confederates to withdraw. Commander F. A. Parker, commanding the Potomac Flotilla, remarked: "It was quite a gallant affair and reflects a great deal of credit upon both the officers and men of the Eureka.
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
A Sunday, April 21, 1861: The "Pawnee War"
John H. Worsham was a member of F Company of the 21st Regiment of Virginia Infantry. In his memoirs written after the war, Worsham recalled these early days of the conflict and an incident he referred to jokingly as the "Pawnee War."
For a week or two before the State seceded, the companies in Richmond were drilling men nearly all the time; a squad of green men at one hour, another squad at the next, so on throughout the entire day; and at night a company drill. Each man was required to report at company headquarters once during the day. The tolling of the fire bells was the signal to meet at the companies' armories, prepared to go wherever ordered.
I was quietly walking home from church, after the morning service on Sunday, April 21, 1861, when the bells commenced to toll. I broke into a run at once, going home as fast as I could. I put on my uniform, etc., and was soon at our armory. Here it was rumored that the gunboat Pawnee was coming up James River, with the intention of capturing or bombarding the city. As soon as all the men reported, the company was formed and marched to Wilton on James River, about ten miles below the city. Passing Rocketts, the port of Richmond, we found the citizens assembled there by thousands; old men, boys, women, girls, women with babies in their arms, in fact nearly the whole population. The fields in Rocketts, as well as the wharves, were literally alive with human beings, commingled with horses and vehicles, as some had ridden down in buggies and carriages. Some had shotguns, some had rifles, some pistols, some swords, some canes, and some had made large piles of stones on the wharves, to use against the enemy. They were all determined that the ship should never get to the wharf. It makes me laugh now, after my experience of war, to think what the citizens were then doing!
We arrived at Wilton about sunset where we were joined by the Richmond Howitzers. A picket from F Company was established along the river. The Howitzers' guns were placed in position. Orders were given to fire on the Pawnee as soon as she came within shooting distance. The men of F Company, not on duty, stacked arms, and were ordered to remain near them during the night. We had nothing to eat, and did not know when or where we would get anything. One of our officers, however, had remained behind, and about eight or nine o'clock that night came up with a wagon loaded with cooked ham, bread, etc., and we had a jolly time over our supper, the first of the war. After eating, the men gathered about in squads talking; finally lying down on the grassy ground and going to sleep; the first experience of the war, and that without either blanket or oilcloth. The night passed without incident; the expected Pawnee did not come. The next day we returned to Richmond on two barges, that were sent down the river for us. We won a great deal of glory in this campaign, as everyone thought we had done wonders. In marching from Rocketts up Main Street to our quarters, which were between Eighth and Ninth Streets, we had an ovation nearly all the way. Thus closed the "Pawnee War."
http://www.civilwar-online.com/2011/04/april-21-1861-pawnee-war.html
B Monday, April 21, 1862: The Confederate Congress passed the Partisan Ranger Act. This law was written to help recruit irregulars to serve in the Civil War. Many men lived and died as Partisan Rangers.
A few survived and lived normal lives after the war, while others never gave up after the war ended. This is a story about the Partisan Rangers, who were also known as “bushwhackers” and “guerillas”, depending on which side of the battle line you were standing.
One of the most famous Rangers roamed the roads of Ray County and thanks to him, our local history is known worldwide.
On Oct. 26, 1864, a company of Missouri Partisan Rangers led by Capt. William Anderson were camped north of present-day Orrick on land owned by “Riley” Blythe, which was then known as Albany.
http://www.richmond-dailynews.com/2011/11/2014-event-will-recreate-bloody-bill%E2%80%99s-death-near-orrick/
C Tuesday, April 21, 1863: Streight’s Raid begins. Union Colonel Abel Streight begins a raid into northern Alabama and Georgia with the goal of cutting the Western and Atlantic Railroad between Chattanooga, Tennessee and Atlanta. The raid ended when Confederate General Nathan Bedford Forrest captured Streight’s entire command near Rome, Georgia.
The plan called for Streight and General Greenville Dodge to move from central Tennessee into northwestern Alabama. Dodge would lead a diversionary attack on Tuscumbia, Alabama, while Streight would take nearly 2,000 troopers across northern Alabama and into Georgia. Streight outfitted his men with mules instead of horses, as he felt they were better adapted to the rugged terrain of the southern Appalachians. The expedition ran into trouble almost immediately when the mules arrived at Nashville in poor condition. A Confederate cavalry detachment swooped in and caused the mules to stampede, and it took two days to round them up.
The first part of the expedition went well. Dodge captured Tuscumbia, and Streight continued east toward Georgia. But on April 29, Streight’s command was attacked by part of General Nathan Bedford Forrest’s cavalry. Streight’s men set a trap for the pursuing Rebels, and it worked well. The Confederate cavalry detachment, led by Captain William Forrest, brother of Nathan Bedford, found itself under fire from two sides. William Forrest was wounded, and the Federals continued on their mission.
But now General Nathan Bedford Forrest was on Streight’s trail, and he would not let up. The Yankees were in hostile territory, and several times the Rebels received important information from local residents that allowed them to gain the upper hand. Finally, Forrest confronted the exhausted Union troops. Under a flag of truce, they discussed terms of surrender on May 3. Forrest had just 600 men, less than half of what Streight now possessed. But Forrest spread his men around the woods. As he met with Streight, couriers from nonexistent units rode up with reports. Streight took the bait, and agreed to surrender. When the Confederates finally emerged to gather the Yankee’s weaponry, the Union colonel realized that he had been had by the crafty Forrest.
http://www.history.com/this-day-in-history/steights-raid-begins
D Thursday, April 21, 1864: U.S.S. Owasco, Lieutenant Commander Henry, seized blockade running British schooner Laura with cargo of guns in the Gulf of Mexico off Velasco, Texas. Boat expedition under Acting Ensign Christopher Carven, U.S.S. Sagamore, took over 100 bales of cotton and destroyed 300 additional bales near Clay Landing, on the Suwannee River, Florida. Boat expedition commanded by Acting Master John K. Crosby from U.S.S. Cimarron destroyed a rice mill and Thursday, April 21, 1864: 5,000 bushels of rice stored at Winyah Bay, South Carolina. The blockaded South could ill afford to lose such food stuffs.
http://www.historycentral.com/navy/cwnavalhistory/April1864.html
FYI CSM Charles Hayden LTC (Join to see) MAJ Dale E. Wilson, Ph.D. SSG Franklin Briant SGT Tiffanie G. SGT Mary G.CPL Ronald Keyes Jr SFC William Farrell SPC Michael Terrell SPC Michael Duricko, Ph.D MAJ Roland McDonald SFC William Farrell SSG Franklin Briant SSG William Jones SSG Michael Noll MCPO Hilary Kunz MAJ Wayne WickizerSGM Hilbert ChristensenCPO William Glen (W.G.) Powell1stSgt Eugene Harless

LTC Stephen F. I think all significant, I am biased but I do like The Pawnee War on the James River to Richmond. Richmond was a unique strategic importance in the Civil War. Great read as usual!

Thanks for sharing