May 5, 1789
The Senate's First Act -- the Oath Act
On May 5, 1789, the Senate passed its first bill -- the Oath Act. That first oath, for members and civil servants, was very simple: "I do solemnly swear that I will support the Constitution of the United States."
Seventy-two years later, the outbreak of the Civil War quickly transformed the routine act of oath-taking into one of enormous significance. At a time of shifting and uncertain loyalties, when members believed the nation had more to fear from northern traitors than southern soldiers, Congress responded with several new oaths. The first one, enacted at the end of the July 1861 emergency session, is nearly identical to the one that members and federal employees take today. In July 1862, during the war's darkest hours, Congress passed a much tougher "Ironclad Test Oath" for civil servants requiring not only a pledge of future loyalty, but also an affirmation of past fidelity. In 1864, the Republican-controlled Senate, over the strenuous objection of the chamber's few Democrats, adopted a rule requiring members to swear to the 1862 Test Oath and, for the first time, to sign a printed copy. The modern practice of senators going to the presiding officer's desk in groups of four to take and sign the oath began in 1864.
For several years after the Civil War, Radical Republicans used the 1862 Test Oath to keep southern Democrats from returning to Congress. In 1868, as the Radicals' power began to wane, Congress passed a separate oath for southern members-elect, but ironically required northerners to continue swearing they had "never voluntarily borne arms against the United States." Finally, in 1884, Congress repealed the Test Oath, leaving the repatriated southerners' oath as the one we know today.
Hyman, Harold M. The Era of the Oath: Northern Loyalty Tests During the Civil War and Reconstruction. Philadelphia: University of Pennsylvania Press, 1954.
Lott, Trent. "The Oath We Take." Congressional Record, January 7, 1997.