Casselton is a city in Cass County, North Dakota, United States. The population was 2,479 at the 2020 census. making it the 20th largest city in North Dakota. Casselton was founded in 1876. The city is named in honor of George Washington Cass, a president of the Northern Pacific Railway, which established a station there in 1876 to develop a town for homesteaders. Casselton is the hometown of five North Dakota governors.