Nygaard taught in the rural schools of Emmons and Steele counties from 1932 to 1935 and was engaged in the grocery and hardware businesses from 1936 to 1960.
He served as mayor of Sharon and as a member of the school board and then as member of the North Dakota House of Representatives from 1949 to 1960. He served as majority leader of that body in 1955 and 1957 and as speaker in 1959. He was a member of the National Monument Commission from 1961 to 1963.