The Commonwealth of Kentucky is a state located in the East Central United States of America. Kentucky is normally included in the group of Southern states (in particular the Upland South), but it is sometimes included, geographically and culturally, in the Midwest.[4][5] Kentucky is one of four U.S. states to be officially known as a commonwealth. Originally a part of Virginia, in 1792 it became the 15th state to join the Union. Kentucky is the 37th largest state in terms of land area, and ranks 26th in population. Kentucky is known as the "Bluegrass State", a nickname based on the fact that bluegrass is present in many of the lawns and pastures throughout the state. It is a land with diverse environments and abundant resources, including the world's longest cave system, the greatest length of navigable waterways and streams in the Lower 48 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, and the nation's most productive coalfield. Kentucky is also known for thoroughbred horses, horse racing, bourbon distilleries, bluegrass music, automobile manufacturing, tobacco, and college basketball.