Sister cities of Louisville, Kentucky

Louisville is the largest city in the Commonwealth of Kentucky and the state's only 1st-class city. In 2010, Louisville proper was the 27th-largest city in the United States. Located beside the Falls of the Ohio, the only major obstruction to river traffic between the Ohio River and the Gulf of Mexico, Louisville first grew as portage site. The city was the headquarters of the Louisville and Nashville Railroad, which grew into a 6,000-mile (9,700 km) system across 13 states. Today, Louisville is best known as the location of the Kentucky Derby, the first of the three annual races that make up the Triple Crown of Thoroughbred Racing. It is the home of the University of Louisville and three of Kentucky's six Fortune 500 companies. Its airport is also the site of UPS's worldwide air hub.

Since 2003, the city's borders have been coterminous with those of Jefferson County because of a city-county merger. The city's total consolidated population at the 2010 census was 741,096. However, the balance total of 602,011 excludes other incorporated places and semi-autonomous towns within the county and is the population listed in most sources and national rankings. As of the 2012, the Louisville metropolitan area (MSA) had a population of 1,334,872 ranking 42nd nationally. The metro area includes Louisville-Jefferson County and 12 surrounding counties, eight in Kentucky and four in Southern Indiana. The Louisville Combined Statistical Area, having a population of 1,451,564, includes the MSA, Hardin County and Larue County in Kentucky, and Scott County, Indiana.