Idaho Counties by Population (2025)

There are 44 counties in Idaho.

Ada County is the largest county in the state, with a population of 536,011. The most recent census shows that its population has increased by 0.08% since the previous census.

A number of other Idaho counties also boast relatively large populations for their state, though not able to match the density of Ada County:

• Canyon County : 271,238
• Kootenai County : 188,450

Idaho Counties with the Fewest Residents

The smallest county in Idaho is Clark County , with a population of just 783. This total represents a decrease of 0.0% since the last census count was performed.

Other small counties include:

• Camas County : 1,358
• Butte County : 2,878
• Lewis County : 3,767

Idaho Counties with Rapid Growth

Camas County , with its current population of 1,358, has shown the largest population growth, with an increase of 0.3% since the last census.

Ada County has also had relatively high population growth of 0.08% with 536,011 residents.

On the other hand, Clark County has had the largest decrease in population, with its 783 current residents totalling 0.0% less than the previous census.