Delegates from Mississippi Territory
On April 7, 1798, the Mississippi Territory was created. A non-voting delegate was elected at-large beginning March 4, 1801.
The area of Mississippi Territory was increased in 1804 and again in 1812.
On December 10, 1817, Mississippi was admitted into the Union as a state and Alabama Territory to the east was spun off.
References
Mississippi Territory's at-large congressional district Wikipedia(Text) CC BY-SA