Elections to the United States House of Representatives were held in Pennsylvania on October 9, 1804, for the 9th Congress.
In the previous election, a delegation of all Democratic-Republicans had been elected to Congress. At this time, a moderate wing of the Democratic-Republican party, known as the Constitutional Republicans or tertium quids ("quids" for short) had broken off from the majority and ran candidates in several districts. The Quids were generally allied with the Federalists.
Pennsylvania was divided into 11 districts, of which four were plural districts with 11 Representatives between them. Several new counties were created between the 1802 elections and the 1804 elections. The districts were:
The borders between the 4th, 5th, and 8th districts were altered slightly in the erection of new counties from parts of several counties
Note: Many of these counties covered much larger areas than they do today, having since been divided into smaller counties
Fifteen incumbents ran for re-election, of whom 14 won. The incumbents Isaac Van Horne (DR) of the , Joseph Hiester (DR) of the and William Hoge (DR) of the did not run for re-election. One seat changed from Democratic-Republican to Federalist.
Returns are incomplete for the , , and districts
William Hoge (DR) of the resigned October 15, 1804. A special election was held November 2, 1804 to fill his seat for the remainder of the 8th Congress
John Hoge was William's brother.
Two special elections were held on October 8, 1805. In the , John A. Hanna (DR) died on July 23, 1805, while in the , John Lucas (DR) resigned prior to the first meeting of the 9th Congress.
Michael Leib (DR) of the resigned February 14, 1806. A special election was held November 27, 1806