Polk County is a county located in the U.S. state of Florida. The county seat is Bartow. Its largest city is Lakeland. Polk County became Florida's 39th county in 1861 and was named in honor of the 11th President of the US James Knox Polk. Polk's economy has three primary industries: citrus, cattle, and phosphate mining. Polk County has a total area of approximately 2,010 square miles of which 93% is land and 7% water. As of the 2000 census, there were 483,924 people, 187,233 households, and 132,373 families residing in Polk County, FL.