Columbia subject headings:
Geographical location codes--Congresses.
United States--Census--Congresses.
Harvard subject headings:
Census districts--United States--Congresses.
United States--Census--Congresses.
United States--Statistical services--Congresses.
Princeton subject headings:
Census districts--United States--Congresses.
United States--Census--Congresses.
United States--Statistical services--Congresses.