From the Guide to 2010 Census State and Local Geography — Montana, History:
The United States acquired the area of Montana from France as part of the Louisiana Purchase in 1803 and by a treaty with Great Britain in 1846. Montana Territory was organized from the northeastern part of Idaho Territory on May 26, 1864, with generally the same boundary as the present state.
Census data for Montana are available beginning with the 1870 census. The 1860 census population in present-day Montana was included in unorganized Dakota, although legally the area was within Nebraska and Washington territories. The portion of Yellowstone National Park in Montana was probably enumerated as part of Wyoming from 1880 to 1910.
Data for the legally established state of Montana are available beginning with the 1890 census.
From QuickFacts: statistics for all states and counties, and for cities and towns with a population of 5,000 or more.
Note: The dashboard shown above is cropped at the bottom. Click on the image to see the full dashboard. Click here to see the table view showing the United States; Montana; Billings city; Missoula city; Great Falls city; and Helena city (state capital).
Sources: 2018 Population Estimates; 2013-2017 American Community Survey, 5-Year Estimates; 2010 Census. Community Facts — Find popular facts (population, income, etc.) and frequently requested data about your community.
Source: 2018 Population Estimates.
Source: 2018 American Community Survey, 1-Year Estimates.
Note: After you create an account, select options for State Export Data (Origin of Movement) or State Import Data (State of Destination) by HS or NAICS. Select State (Montana) and Measures, Commodity, Country and/or Time for data. For more information, see Quick Start Guide.
Sources: 2014 Population Estimates and 2014 American Community Survey, 1-Year Estimates.
Sources: 2009-2013 American Community Survey, 5-Year Estimates, 2012 Survey of Business Owners and other federal data.
Source: 2012 Economic Census. The Census Bureau will release 2017 Economic Census statistics from September 2019 through 2021.