Tulare County is a county in the U.S. state of California. As of the 2010 census, the population was 442,179. Its county seat is Visalia. The county is named for Tulare Lake, once the largest freshwater lake west of the Great Lakes.Drained for agricultural development, the site is now in Kings County, which was created in 1893 from the western portion of the formerly larger Tulare County.arts of the county's territory were given to Fresno County in 1856, to Kern County and to Inyo County in 1866 and to Kings County in 1893. The infectious disease Tularemia caused by the bacterium Francisella tularensis is named after Tulare County.