Norwegian Americans: U.S. Census
For many family history researchers the 1900 U.S. Census is of tremedous help. That is the first Census that gives the year of immigration, which can be very helpful in getting ones ancestor back to the "old country".
Emigration records from Norway start 1867. Therefore these U.S. Census (1850 & 1860) records can be of great help in identifying ones Norwegian ancestors already here in America.