In the Tampa Bay Region of Florida, Hillsborough County was formed in 1834 from Alachua and Monroe counties. In 1855, the southern part of Hillsborough became Manatee County; in 1861, the eastern part was split off to help form Polk County; and in 1911, the western part became Pinellas County. Its county seat, Tampa, is on I-75 at the terminus of I-4, and is about 80 miles southwest of Orlando. Hillsborough is bordered by Tampa Bay and the counties of Pasco, Polk, Manatee and Pinellas.