What are the largest counties in Idaho?

Ada County is the largest county in Idaho, with 546,141 residents in 2025 (Census PEP). Canyon County (275,123) and Kootenai County (191,864) come next.

Data as of 2025 · updated November 5, 2026

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43 of 44 Idaho counties ranked (1 is too small to rank)

Idaho counties ranked by population
Rank	County	Residents 2025	Change 2020–25
1	Ada County	546,141	+9.6%
2	Canyon County	275,123	+18.1%
3	Kootenai County	191,864	+11.0%
4	Bonneville County	135,771	+8.9%
5	Twin Falls County	97,539	+7.9%
6	Bannock County	91,591	+4.9%
7	Madison County	55,172	+4.2%
8	Bonner County	54,420	+14.8%
9	Bingham County	51,153	+6.4%
10	Nez Perce County	42,905	+1.8%
11	Latah County	41,842	+5.6%
12	Jefferson County	35,297	+13.6%
13	Elmore County	29,465	+2.8%
14	Payette County	27,824	+8.8%
15	Cassia County	26,397	+6.6%
16	Jerome County	26,362	+8.6%
17	Blaine County	25,517	+4.8%
18	Minidoka County	22,911	+5.7%
19	Gem County	21,773	+13.0%
20	Idaho County	17,874	+7.7%
21	Gooding County	16,446	+5.1%
22	Franklin County	15,889	+11.2%
23	Fremont County	14,208	+5.9%
24	Shoshone County	14,130	+7.1%
25	Boundary County	13,997	+15.3%
26	Teton County	13,254	+12.9%
27	Valley County	12,831	+8.4%
28	Owyhee County	12,661	+5.6%
29	Washington County	11,583	+9.7%
30	Benewah County	10,508	+9.7%
31	Clearwater County	9,118	+4.1%
32	Boise County	8,545	+11.5%
33	Lemhi County	8,474	+6.5%
34	Power County	8,246	+4.6%
35	Caribou County	7,252	+3.4%
36	Bear Lake County	6,727	+5.7%
37	Lincoln County	5,603	+9.1%
38	Oneida County	5,085	+11.4%
39	Adams County	5,013	+13.3%
40	Custer County	4,636	+8.6%
41	Lewis County	3,704	+4.8%
42	Butte County	2,783	+7.8%
43	Camas County	1,316	+21.7%

How this is ranked

The Census Bureau's July 1 resident population estimates for 2025, largest first, with the change since 2020. Counties with fewer than 1,000 residents are not ranked. Areas without an estimate for the same year as the others are not ranked.

Source: U.S. Census Bureau, Population Estimates Program (Vintage 2025). Figures come from public federal statistics and are informational only, not investment advice. Check the source before relying on a number. Methodology: how ranks and figures are built.

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Questions

What is the largest county in Idaho?

Ada County is the largest county in Idaho, with 546,141 residents in 2025 (Census PEP). Canyon County (275,123) and Kootenai County (191,864) come next.

How is this ranking calculated?

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