That sign is from Northland Oil Company. Like T-way mentioned, they are out of St. Paul, MN. The company was founded in 1917 and it was bought out in 1944 and became Northland Products Company. They are still in business today.
This info was located on Scott Benjamin’s globe CD, which I highly recommend you buy. It has more detailed info on Northland and the history of most every other oil company.