Union City is a borough in Erie County, Pennsylvania, United States, located 26 miles (42 km) southeast of Erie. In the twentieth century, there were three large chair factories, planing and grist mills, a powdered milk plant, and several furniture factories. In 1900, 3,104 people lived here, and in 1910, 3,684 people lived here. The population was 3,163 at the 2010 census.