Franklin County is a county located in the U.S. state of Washington. As of the 2010 census, its population was 78,163. The county seat is at Pasco, which is also the county's largest city. It was named after Benjamin Franklin. Franklin County was formed out of Whitman County on November 28, 1883.
According to the U.S. Census Bureau, the county has a total area of 1,265 square miles (3,276.3 km2), of which 1,242 square miles (3,216.8 km2) is land and 23 square miles (59.6 km2) (1.81%) is water.