Union is a town in Tolland County, Connecticut, United States. The population was 854 at the 2010 census, making it the least populous town in Connecticut and the second-least populous municipality in Connecticut; only the Borough of Fenwick has fewer people. Union includes the village of Mashapaug located in the Eastern Uplands at the Massachusetts state line. Also, Union is located 33 miles(55 km) northeast of the state capital, Hartford and 67 miles(108 km) southwest of Boston as well as 153 miles (240 km) northeast of New York City.