Great Britain’s Gift of the Magna Carta to the United States | US House of Representatives:...

On June 3, 1976, the United States was presented with the oldest known copy of Magna Carta for a one year loan for the Bicentennial Celebration. From the article:

"Great Britain’s Gift of the Magna Carta to the United States
May 26, 1976
Great Britain’s Gift of the Magna Carta to the United States
Collection of the U.S. House of Representatives, Jim Oliver Collection
About this object
The returning ceremony of the Magna Carta was held on June 13, 1977.
On this date, a U.S. congressional delegation to Great Britain received a gold-embossed reproduction of the Magna Carta in honor of the bicentennial of the United States. In an elaborate ceremony at Westminster Hall in London, the British Parliament bestowed a replica of the Magna Carta to House and Senate leaders, including Speaker of the House Carl Albert of Oklahoma, House Majority Leader Thomas P. “Tip” O’Neill of Massachusetts, and Senate Majority Leader Mike Mansfield of Montana. Considered the seminal document in British constitutional history and a major inspiration for the American Declaration of Independence, the original Magna Carta, signed by King John of England in 1215, called for restrictions on royal authority and outlined a series of rights which became the foundation for common law. “Nothing could be more symbolically important to the people of the United States,” Speaker Albert concluded upon receiving the document on behalf of the delegation and the U.S. Congress. “Had there been no Magna Carta in 1215, there would have been no Declaration of Independence in 1776.” In a continued celebration of the common roots shared by Great Britain and the United States, representatives from England traveled to the Capitol on June 3, 1976, to present Congress with an additional gift: a one-year loan of the oldest-known original copy of the Magna Carta. During the ceremony in the Capitol Rotunda, Speaker Albert called the gesture “the most significant part of our Bicentennial celebration, because it means that our Capitol will house, out of the generosity of the British Parliament, the most important single political document in the long history of the English-speaking nations.” After one year on display in the Rotunda, the prized document returned to the British Museum and was replaced with the replica given to Congress in honor of the Bicentennial."