The Commonwealth of Kentucky, known as the Bluegrass State, spans 40,409 square miles and is bordered by seven states in the center of the eastern US. With a population of 4,241,474 (2007), Kentucky is diverse in geography, industry, and history. Kentucky's capital, Frankfurt, located in the center of the state, is often confused with its largest city, Louisville. Home to caves in the western part of the state, several military facilities including Fort Knox, automobile manufacturers, the Cumberland Gap and the Appalachian mountains in the southeastern part of the state, and several large horse farms, Kentucky is rich in heritage and attractions.