Union is a city in and the county seat of Franklin County, Missouri, United States. The population was 7,757 at the 2000 census. It is located on the Bourbeuse River. The city was founded in 1827 and is named after the ideal of political unity.
Union is located at 38°26′48″N 91°0′22″W / 38.44667°N 91.00611°W / 38.44667; -91.00611 (38.446684, -91.006070). According to the United States Census Bureau, the city has a total area of 8.1 square miles (20.9 km²), all of it land.
As of the census of 2000, there were 7,757 people, 2,940 households, and 2,002 families residing in the city. The population density was 959.9 people per square mile (370.7/km²). There were 3,133 housing units at an average density of 387.7 per square mile (149.7/km²). The racial makeup of the city was 96.44% White, 1.43% African American, 0.30% Native American, 0.17% Asian, 0.23% from other races, and 1.43% from two or more races. Hispanic or Latino of any race were 0.99% of the population.