Representatives had been elected in April 1802 to a term in the 8th United States Congress beginning on March 4, 1803.

Daniel D. Tompkins, elected in the 2nd/3rd D., was appointed on July 2, 1804, to the New York Supreme Court and resigned his seat, before the congressional term began.

A special election to fill the vacancy was held in October 1804, and was won by Gurdon S. Mumford, of the same party.

Samuel L. Mitchill, who had been re-elected in the 2nd/3rd D. to a third term, resigned his seat on November 22, 1804, after his election to the U.S. Senate.

[10] The House of Representatives of the 9th United States Congress met for the first time at the United States Capitol in Washington, D.C., on December 2, 1805, and Blake, Halsey, Masters, Mumford, Russell, Sailly, Sammons, Schuneman, Thomas, Tracy, Van Rensselaer and Williams took their seats on this day.