Falls County is a county located in the U.S. state of Texas. As of the 2010 census, its population was 17,866. The county seat is Marlin. It is named for the original 10-foot-tall waterfall on the Brazos River, which existed until the river changed course during a storm in 1866. The present falls can be found two miles northeast of the original falls, at the Falls on the Brazos Park, a camping site located only a few miles out of Marlin on Farm to Market Road 712.