April 2023: The 1803 Louisiana Purchase
...territory that became the state of Montana in 1889 had a population of 20,595...1740s French Fort de Cavagnal—in present-day Leavenworth County, KS; the French
https://www.census.gov/about/history/stories/monthly/2023/april-2023.html
Tallies
...and Blocks by State Tallies of Counties, County Subdivisions, and Places by State...Tallies of Geographic Entities by County Tallies of Tribal Tracts and Tribal
https://www.census.gov/geographies/reference-files/2000/geo/tallies.html
2017 Census of Governments
.... . . . . . . . . . . . . . . 168 Montana . . . . . . . . . . . . . . . . .... . 310 Appendixes A. County-Type Areas Without County Government . . . . .
https://www.census.gov/content/dam/Census/library/publications/2017/econ/2017isd.pdf