Career
Born in Trondenes, he was elected to the Norwegian Parliament from the Market towns of Nordland, Troms and Finnmark in 1937, and was re-elected on two occasions. Nilsen held various positions in Narvik city council from 1925 to 1940 and 1945 to 1960, serving as mayor in the periods 1945–1947 and 1947–1951.