12th most populous of 44
With 34,854 residents in 2024, Jefferson County ranks 12th by population among Idaho's 44 counties and is home to 1.7% of the state's residents.

Jefferson County has the 4th highest median household income in Idaho ($86,679) and the 4th youngest population (median age 32.8).
Jefferson County is home to 34,854 people (2024 estimate) on 1,094 square miles of land. This page brings together official U.S. Census Bureau population estimates since 2000, the components of change—births, deaths and migration—American Community Survey indicators on income, housing, poverty and education, BEA economic accounts and BLS unemployment.
Pick an indicator to see its long-run evolution.
U.S. Census Bureau: intercensal estimates 2000–2009, Vintage 2020 (2010–2019) and Vintage 2024 (2020–2024), July 1.
| Indicator | Value | Year and source |
|---|---|---|
| Population estimate | 34,854 | 2024 · U.S. Census Bureau |
| Population, 2010 Census | 26,140 | 2010 · U.S. Census Bureau |
| Population, 2000 | 19,193 | July 1, 2000 · Census intercensal |
| Change since 2000 | +81.6% | 2000–2024 · Census |
| International migration | +69 | 2024 · Census Vintage 2024 |
| Domestic migration | +281 | 2024 · Census Vintage 2024 |
| Birth rate | 13.6 per 1,000 | 2024 · calculated |
| Death rate | 6.4 per 1,000 | 2024 · calculated |
| Population rank in Idaho | 12th of 44 | 2024 · calculated |
| Per capita personal income | $50,258 | BEA, 2024 · official |
| Gross domestic product | $1.4 billion | BEA, current dollars, 2024 · official |
| Median household income | $86,679 | ACS 2020–2024 5-year · official |
| Poverty rate | 9.7% | ACS 2020–2024 5-year · official |
| Bachelor’s degree or higher | 27.4% | Age 25+, ACS 2020–2024 5-year · official |
| Foreign-born residents | 4.2% | ACS 2020–2024 5-year · official |
| Median home value | $408,400 | ACS 2020–2024 5-year · official |
| Median gross rent | $1,138/month | ACS 2020–2024 5-year · official |
| Median age | 32.8 years | ACS 2020–2024 5-year · official |
| Households | 10,199 | ACS 2020–2024 5-year · official |
| Owner-occupied homes | 83.0% | ACS 2020–2024 5-year · official |
Comparable indicators for Jefferson County, Idaho and the United States.
| Indicator | County | Idaho | U.S. | Reference |
|---|---|---|---|---|
| Population change 2020–2024 | +12.8% | +8.8% | +2.6% | Census Vintage 2024 |
| Birth rate (per 1,000) | 13.6 | 11.4 | 10.6 | 2024 |
| Death rate (per 1,000) | 6.4 | 8.3 | 9.1 | 2024 |
| Net migration rate (per 1,000) | 10.0 | 12.1 | 8.2 | 2024 |
| Population density (/mi²) | 31.9 | 24.2 | 96.3 | 2024 |
| Per capita personal income | $50,258 | $62,323 | $73,204 | BEA, 2024 |
| Median household income | $86,679 | $77,800 | $80,734 | ACS 2020–2024 5-year |
| Poverty rate | 9.7% | 10.6% | 12.5% | ACS 2020–2024 5-year |
| Bachelor’s degree or higher | 27.4% | 31.8% | 35.7% | Age 25+, ACS 2020–2024 5-year |
| Foreign-born residents | 4.2% | 5.9% | 14.1% | ACS 2020–2024 5-year |
| Median home value | $408,400 | $418,600 | $332,700 | ACS 2020–2024 5-year |
| Median gross rent | $1,138/month | $1,238/month | $1,413/month | ACS 2020–2024 5-year |
| Median age | 32.8 years | 37.3 years | 38.9 years | ACS 2020–2024 5-year |
| Owner-occupied homes | 83.0% | 72.1% | 65.2% | ACS 2020–2024 5-year |
With 34,854 residents in 2024, Jefferson County ranks 12th by population among Idaho's 44 counties and is home to 1.7% of the state's residents.
Its population went from 19,193 in 2000 to 34,854 in 2024, a change of +81.6%, compared with +54.0% for Idaho as a whole.
In the year to July 2024 the county recorded 473 births and 223 deaths, so births outnumbered deaths by 250.
Annual Census estimates since 2000 put the county's highest population in 2024, at 34,854.
Jefferson County has about 31.9 residents per square mile of land, ranking 13th of 44 counties; Idaho averages 24.2.
With a median household income of $86,679 (ACS 2020–2024 5-year), the county ranks 4th of 44 Idaho counties; the state median is $77,800.
Its economy produced $1.4 billion of GDP in 2024 (BEA), 18th largest among 44 Idaho counties.
Real GDP fell 0.6% in 2024, adjusted for inflation (BEA, chained 2017 dollars).