Illinois Territory's at-large congressional district

Illinois Territory's at-large congressional district was a congressional district that encompassed the entire Illinois Territory. The territory was established on March 1, 1809 from portions of Indiana Territory. The district elected a non-voting delegate to the United States House of Representatives.

Statehood
On April 18, 1818, Congress passed an act that enabled the people of Illinois Territory to begin the process of forming a state. As part of that act, Illinois Territory was reduced in size to the boundaries of the present state. The remainder of what had been Illinois Territory was attached to Michigan Territory. The state of Illinois was accepted into the Union on December 3, 1818.