Union is a home rule-class city in Boone County, Kentucky, United States. The population was 5,379 as of the 2010 United States Census. The area was rural until residential growth in the 1990s and 2000s. Union is located 17 miles southwest of Cincinnati, Ohio.
The City of Union grew from a small settlement that may have existed as early as the late 1700s. By the early 1800s, much of the land that now lies in Union was owned by the Fowler family, and Benjamin Piatt Fowler had a home in what is now the northern area of the city c. 1817.
Union was established as early as 1833, and was officially incorporated as a city in 1838. The name "Union" is said to have been chosen since it was a connection point between the city of Florence and Big Bone Lick. Salt was manufactured at Big Bone Lick during the early 1800s, and was brought to Union for distribution to other area settlements.
A post office was in operation by 1850, and at some point there was a Millinery Shop located next to the post office.