Idaho decennial census population

Publisher

Organization

U.S. Census Bureau

Publisher’s dataset

Decennial Census population counts

File or API used

https://www2.census.gov/library/publications/2003/dec/phc-3-14.pdf

Retrieval script

scripts/fetch-census-decennial.py

Methodology

https://www.census.gov/programs-surveys/decennial-census/about/history.html

Coverage

Geography

Idaho and its 44 counties

Time coverage

1870-2020

Update frequency

Decennial

Published

March 26, 2026

Retrieved

September 8, 2026

License

The compiled file on this page is CC BY 4.0. The underlying records: Public domain. U.S. federal government work.

Measures

Caveats

• State totals for 1870-2000 are from PHC-3-14, "Population and Housing Unit Counts, Idaho: 2000" (U.S. Census Bureau, issued September 2003), Table 1. State totals for 2010 and 2020 are from the Census Bureau's 2020 Census apportionment product, apportionment.csv, released 2026-03-26 (its historical table also carries 1910-2000, not used here since PHC-3-14 already covers those years).
• County totals are available for 1960, 1970, 1980, 1990 and 2000 from PHC-3-14 Table 2, and for 2010 and 2020 from the Population Estimates Program's CENSUS2010POP and ESTIMATESBASE2020 columns (co-est2019-alldata.csv and co-est2025-alldata.csv, the same files census-pep.json cites). County population for 1870-1950 was skipped: the only Census Bureau file found that tabulates all 44 counties that far back, "Population of States and Counties of the United States: 1790-1990" (March 1996), is a scan of a 1996 report whose OCR text could not be reliably aligned to a census year for every county, so it was not used rather than risk shipping a wrong figure.
• 2020 county values are the Population Estimates Program's April 1, 2020 estimates base (ESTIMATESBASE2020), the Bureau's own postcensal representation of the 2020 Census count, not the originally tabulated redistricting file; every 2020 county observation carries a note to this effect. The gap is small: statewide, this base is 1,839,123 against the 1,839,106 officially delivered for apportionment (see disagreements).
• Some individual county and state figures were later revised by the Census Bureau from what was originally published for that census; PHC-3-14 flags these with an 'r' in its own tables, and this dataset carries the revised figure with a note, not the original.

Where sources disagree

• population.decennial_count, 16, 1970: U.S. Census Bureau, Population of States and Counties of the United States: 1790-1990 (March 1996) publishes 712567. This dataset uses PHC-3-14's 713,015. The 1996 compilation, and the 2020 Census apportionment product's historical table, both give 712,567 for the same census.
• population.decennial_count, 16, 1980: U.S. Census Bureau, Population of States and Counties of the United States: 1790-1990 (March 1996) publishes 943935. This dataset uses PHC-3-14's 944,127. The 1996 compilation, and the 2020 Census apportionment product's historical table, both give 943,935 for the same census.
• population.decennial_count, 16, 1990: U.S. Census Bureau, Population of States and Counties of the United States: 1790-1990 (March 1996) publishes 1006749. This dataset uses PHC-3-14's 1,006,734, itself marked as a post-hoc revision in that table. The 1996 compilation, and the 2020 Census apportionment product's historical table, both give 1,006,749 for the same census.
• population.decennial_count, 16019, 1970: U.S. Census Bureau, Population of States and Counties of the United States: 1790-1990 (March 1996) publishes 51250. This dataset uses PHC-3-14 Table 2's 52,457 for Bonneville County. The 1996 compilation gives 51,250 for the same census; this is one of the pre-1960 figures in that scanned report this dataset otherwise chose not to rely on.

Pages built on this dataset

• Idaho population history

Downloads

CSV · JSON. 324 observations, 1870-2020.

How to cite

Understand Idaho, “Decennial Census population counts”, compiled from U.S. Census Bureau, Decennial Census population counts. Retrieved September 8, 2026. https://understandidaho.com/data/census-decennial/. CC BY 4.0.

Cite U.S. Census Bureau directly for the figures themselves.