The 9th United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the United States Senate and the United States House of Representatives. It met in Washington, D.C., from March 4, 1805, to March 4, 1807, during the fifth and sixth years of Thomas Jefferson's presidency. The apportionment of seats in the House of Representatives was based on the 1800 United States census. Both chambers had a Democratic-Republican majority.

The 8th United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the United States Senate and the United States House of Representatives. It met in Washington, D.C. from March 4, 1803, to March 4, 1805, during the last two years of Thomas Jefferson's first term in office. The apportionment of seats in the House of Representatives was based on the 1800 United States census. Both chambers had a Democratic-Republican majority.