Newton is a city in and the county seat of Harvey County, Kansas, United States. As of the 2020 census, the population of the city was 18,602. Newton is located 25 miles (40 km) north of Wichita. The city of North Newton. located immediately north, exists as a separate political entity. Newton is located at the intersection of Interstate 135, U.S. Route 50, and U.S. Route 81 highways.