Union is a city in Boone County, Kentucky, United States. The population was 5,379 in the 2010 Census. Previously a small rural community, the city began to experience rapid residential development in the 1990s and 2000s and has now become one of Cincinnati's more affluent suburbs.

The City of Union grew from a small settlement that may have existed as early as the late 18th century. However by the early 19th century, much of the land that now lies in Union was owned by the Fowler family, and Benjamin Piatt Fowler built his in what is now the northern area of the city c. 1817.

It has been recorded that Union was established as early as 1833, but existing documentation shows that Union was officially incorporated as a city in 1838. Why the name Union was chosen no one actually knows, but the story goes that since it was a connection point between Florence, KY and Big Bone Lick, "Union" seemed somehow appropriate. Salt was manufactured at Big Bone Lick during the early 19th century, and then brought to Union for distribution to other area settlements.

Kentucky (ⁱ/kɨnˈtʌki/), officially the Commonwealth of Kentucky, is a state located in the Upper South of the United States. Kentucky is one of four U.S. states constituted as a commonwealth (the others being Virginia, Pennsylvania, and Massachusetts). Originally a part of Virginia, in 1792 Kentucky became the 15th state to join the Union. Kentucky is the 37th most extensive and the 26th most populous of the 50 United States.

Kentucky is known as the "Bluegrass State", a nickname based on the fact that bluegrass is present in many of the pastures throughout the state, because of the fertile soil. It made possible the breeding of high-quality livestock, especially thoroughbred racing horses. It is a land with diverse environments and abundant resources, including the world's longest cave system, Mammoth Cave National Park; the greatest length of navigable waterways and streams in the contiguous United States; and the two largest man-made lakes east of the Mississippi River. It is also home to the highest per capita number of deer and turkey in the United States, the largest free-ranging elk herd east of Montana, and the nation's most productive coalfield. Kentucky is also known for horse racing, bourbon distilleries, bluegrass music, automobile manufacturing, tobacco and college basketball.