Census Office is a valid heading for U.S. censuses up to and including the twelfth (1900); the thirteenth census (1910) and those subsequent were conducted by the Bureau of the Census

National Archives, via WWW, Mar. 1, 2011: Records of the Bureau of the Census (Census Office; the term refers to temporary staffs established to administer the decennial censuses, 1790-1900; censuses were taken by U.S. district marshals, 1790-1870; and by enumerators under supervisors responsible through the Superintendent of the Census to the Secretary of the Interior, 1880-1900)