Riverdale is a town in McLean County, North Dakota in the United States. The population was 273 at the 2000 census. Riverdale was the largest of the construction camps that sprang up in 1946 to house workers building the Garrison Dam just to the west. After the dam was completed in 1953, residents of the other camps (including Dakota City and Big Bend) who decided to stay on relocated to Riverdale. It was operated directly by the federal government from its founding until 1986 when it was finally turned over to the state of North Dakota and incorporation followed shortly afterwards.