Union is a city in Montgomery and Miami Counties in the U.S. state of Ohio. The population was 6,419 at the 2010 census. It is part of the Dayton Metropolitan Statistical Area.GeographyThe coordinates for The City of Union are .According to the United States Census Bureau, the city has a total area of 7.13sqmi, of which 7.05sqmi is land and 0.08sqmi is water. The Stillwater River runs on its east side.Ironically, Union lies west of West Union, Ohio, the county seat of Adams County approximately 60 miles east of Cincinnati. Union and West Union are not adjacent to each other, actually being approximately 120 miles from each other.TransportationOne major state highway, State Route 48, runs North and South through Union. In Union, State Route 48 is known as Main Street. Union is 4 miles North of Interstate 70Other notable streets in Union include Martindale Road, Sweet Potato Ridge Road, and Phillipsburg-Union Road.GovernmentUnion is a charter city and has a mayor/council/manager form of government. The current mayor is Michael O'Callaghan, and John P. Applegate is Union's City Manager.Demographics2010 censusAs of the census of 2010, there were 6,419 people, 2,554 households, and 1,811 families residing in the city. The population density was 910.5PD/sqmi. There were 2,721 housing units at an average density of 386.0/sqmi. The racial makeup of the city was 93.5% White, 3.6% African American, 0.2% Native American, 0.7% Asian, 0.2% from other races, and 1.8% from two or more races. Hispanic or Latino of any race were 1.6% of the population.