The 10th United States Congress was a meeting of the legislative branch of the United States federal government, consisting of the Senate and the House of Representatives. It met in Washington, D.C. from March 4, 1807, to March 4, 1809, during the seventh and eighth years of Thomas Jefferson's presidency. The apportionment of seats in the House of Representatives was based on the 1800 census; both chambers had an overwhelming Democratic-Republican majority.

The Territory of Illinois was an organized incorporated territory of the United States that existed from March 1, 1809, until December 3, 1818, when the southern portion of the territory was admitted to the Union as the State of Illinois. Its capital was the former French village of Kaskaskia (which is still a part of the State of Illinois). The northern half of the territory, modern Wisconsin and parts of modern Minnesota and Michigan became part of the Territory of Michigan.