Mount Vernon is a city in Grant County, Oregon, United States.

Its post office was established in 1877 and named after a black stallion that belonged to settler David W. Jenkins.

The stallion's stable, a small stone building, is still standing in a field on the north side of U.S. Highway 26 about 2.2 miles (3.5 km) east of the main intersection in town.

[7] In 1915 the ranching community had a population of 60 and a hotel at a hot springs resort approximately 2 miles (3.2 km) north.

[6] According to the United States Census Bureau, the city has a total area of 0.68 square miles (1.76 km2), all land.

34.7% of all households were made up of individuals, and 18.1% had someone living alone who was 65 years of age or older.

29.4% of all households were made up of individuals, and 12.5% had someone living alone who was 65 years of age or older.