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 stone building about 1.5 miles (2.4 km) east of town, was still standing in 1990. In 1915 the ranching community had a population of 60 and a hotel at a hot springs 2 miles (3.2 km) north, and the population had grown to 451 by the 1950 census. There are a few motels and restaurants in Mount Vernon.