Falls City is a city in and the county seat of Richardson County, Nebraska, United States. The population was 4,133 at the 2020 census, down fr…Falls City is a city in and the county seat of Richardson County, Nebraska, United States. The population was 4,133 at the 2020 census, down from 4,325 in 2010 and 4,671 in 2000. The site of Falls City is located on the north side of the Big Nemaha River, in the southeast corner of the state. The river in 1857 had banks and bed of rock and stone. The town was located near where the river flowed over a four-foot rock ledge called the "Falls of Nemaha", for which the town was named. Over time the river has changed to the extent that the falls no longer exist.