On the banks of the Ohio River, Louisville is America's southernmost northern city and its northernmost southern city. Victorian mansions blend well with contemporary skyscrapers here in Kentucky's largest city. Founded in 1778, Louisville was incorporated in 1780 after then-governor of Virginia Thomas Jefferson signed the town charter. The city is located on the Falls of the Ohio, the only navigational barrier on the entire length of the Ohio River. Louisville has historically been an important transportation center and is the home of many enduring American institutions, including Churchill Downs, site of the world-famous Kentucky Derby, and the Louisville Slugger baseball bat factory. The city of Louisville merged with Jefferson County on January 6, 2003, effectively increasing the city's population from just over 250,000 to more than 550,000 residents. Eighty-three previously incorporated suburban communities within Jefferson County retain some autonomy under the combined Louisville-Jefferson County government, and are not included the city's population. Louisville maintains active sister city relationships with Jiujiang , China, La Plata , Argentina, Mainz , Germany, Montpellier , France, Perm , Russia, Quito , Ecuador, and Tamale , Ghana.