Mount Vernon is a city in and the county seat of Jefferson County, Illinois, United States. The population was 15,277 at the 2010 census.
Mount Vernon is the principal city of the Mount Vernon Micropolitan Statistical Area, which includes all of Jefferson and Hamilton counties.
Mt. Vernon was founded in 1817 by Zadok Casey, who was elected to the State Senate in 1822 and was elected Lieutenant Governor in 1833. He served in the U.S. Congress between 1833 and 1843. The town was named for George Washington's plantation, Mount Vernon, which was named for Edward Vernon, a British naval hero.
When the town was founded, there was no road to it. Travelers had to get there by either following the high ground from the north or crossing the swamps from the south. In the early 19th century the Goshen Road crossed Illinois in a northwesterly direction from Old Shawneetown, Illinois to the Goshen Settlement, near what is now Edwardsville.