Selfridge is a city in Sioux County, North Dakota in the United States. Selfridge was founded in 1912. The population was 223 at the 2000 census. A December 2009 estimate puts it at 619. 164 families reside in the area. The city is the 3rd largest city on the Standing Rock Indian Reservation. Towns that border this city are Chadwick, ND and Porcupine, North Dakota, these towns act as suburbs and subdivisions of the city.