First Republican national convention ends

On June 17-19, 1856, the Republican Party had its first national convention in Philadelphia. From the article:

"First Republican national convention ends
In Music Fund Hall in Philadelphia, the first national convention of the Republican Party, founded two years before, comes to its conclusion. John Charles Fremont of California, the famous explorer of the West, was nominated for the presidency, and William Dewis Dayton of New Jersey was chosen as the candidate for the vice presidency.

In 1854, Congress moved to vote on the Kansas-Nebraska Bill, an act that would dissolve the terms of the Missouri Compromise of 1820 and allow slave or free status to be decided in the territories by popular sovereignty. When it seemed the bill would win congressional passage, the Whig Party, which could not adequately cope with the issue of slavery, disintegrated. By February 1854, anti-slavery factions of the former Whig Party had begun meeting in the upper Midwestern states to discuss the formation of a new party. One such meeting, at Ripon, Wisconsin, on March 20, 1954, is generally remembered as the founding meeting of the Republican Party.

The Republicans, who called for the abolition of slavery in all U.S. territories, rapidly gained supporters in the North, and in 1856 their first presidential candidate, John Fremont, won 11 of the 16 Northern states. By 1860, the majority of Southern states were publicly threatening secession if a Republican won the presidency. On November 6, 1860, Republican Abraham Lincoln was elected president over a divided Democratic Party, and six weeks later South Carolina formally seceded from the Union. Within six more weeks, five other Southern states had followed South Carolina’s lead. On April 12, 1861, the Civil War began when Confederate shore batteries under General P.G.T. Beauregard opened fire on Fort Sumter in South Carolina’s Charleston Bay.

The Civil War firmly identified the Republican Party as the official party of the victorious North. After the war, the Republican-dominated Congress forced a radical Reconstruction policy on the South, which saw the passage of the 13th, 14th, and 15th Amendments to the Constitution, abolishing slavery and granting voting rights to African American men in the South. By 1876, the Republican Party had lost control of the South, but it continued to dominate the presidency, with a few intermissions, until the ascendance of Franklin D. Roosevelt in 1933."