Easton is a city in Buchanan County, Missouri, United States. The population was 227 at the 2020 census. It is part of the St. Joseph, M…Easton is a city in Buchanan County, Missouri, United States. The population was 227 at the 2020 census. It is part of the St. Joseph, MO–KS Metropolitan Statistical Area. Easton was platted in 1854. The name Easton may be directional, for the community lies east of St. Joseph. A post office called Easton has been in operation since 1855.