The early U.S. Territorial Period was 1821-1845, but the eventual Territorial Period lasted until 1912, when Arizona and New Mexico were admitted as states.
Where can you find territorial records?
I would suggest searching the online catalogs for these types of repositories, using the search term “territorial papers.”
- State archives and libraries
- National Archives Regional Branches
- The Family History Library in Salt Lake City. Do a “keyword” search for “territorial papers” in the FamilySearch online catalog.
- State level genealogical and historical societies
- University Special Collections in the state you are researching
- Territorial records can also be found on the county level sometimes
Here is a quick guide and links to the territorial papers available at the Family History Library:
- State Department territorial papers, Arizona, 1864-1872, FHL film 1580035
- State Department territorial papers: Colorado series, FHL film 1464017
- Territorial papers, Idaho, 1863-1872 FHL film 1580038
- Territorial papers of Montana, 1864-1872, FHL films 1602228 -9
- State department territorial papers, Nevada, 1861-1864 FHL film 1491200
- State department territorial papers: New Mexico, 1851-1972, FHL films 1580030-33
- State Department territorial papers, Utah series, FHL film 491567
- Interior Department territorial papers, Utah, 1850-1902, FHL films 1602234 -9
- Territorial papers of Wyoming, 1868-1873, FHL film 1602230
Here are some published finding aids for territorial records:
Kvasnicka, Robert M. The Trans-Mississippi West, 1804-1912: A Guide to Federal Records for the Territorial Period, pts. I-IV (Washington, District of Columbia : National Archives and Records Administration, c1993-1996).
Chiorazzi, Michael. Pre-Statehood Legal Materials: A Fifty-State Research Guide, including New York City and the District of Columbia, 2 volumes (New York : The Haworth Information Press, 2005).
Some other good resources are:
United States, The public statutes at large of the United States of America / by authority of Congress (Boston : Little, Brown, n.d.)
United States. Congress. House and Senate Documents and Reports, United States Congressional Serial Set (Washington : U.S. G.P.O., n.d.).
United States. Congress, American State Papers, 38 vol (Buffalo, N. Y. : W.S. Hein, 1998)