Mount Vernon is the county seat of and the most populous city in Skagit County, Washington, United States. A central location in the Skagit River Valley, the city is located 51 miles south of the U.S.–Canada border and 60 miles north of Seattle. The population was 35,219 at the 2020 census, making it the 35th most-populous city in Washington, with 62,966 people living in its urban area.