Polk County is a county located in the U.S. state of Florida. Its 2010 population was 602,095. Its county seat is Bartow and its largest city is Lakeland. Polk County is coextensive with the Lakeland-Winter Haven, Florida Metropolitan Statistical Area. Located in central Florida along the I-4 Corridor, Polk, along with the counties to the west, is sometimes considered a part of the Tampa Bay Area.