34,854 people (2024 Census estimate, +12.1% since 2020)
1,094 square miles of land · 32 people per square mile
“Highest” and “lowest” are just order, not grades: a high rank for poverty or hazard losses means more of it. Each figure's source is in its section below.
17 active community water systems list Jefferson County in the area they serve, reporting 9,339 people served in all (a system that crosses county lines counts its whole population).
| RIGBY CITY OF groundwater · local government · ID7260032 | 5,400 served |
| ROBERTS CITY OF groundwater · local government · ID7260035 | 680 served |
| RIRIE CITY OF groundwater · local government · ID7260034 | 656 served |
| MORNING VIEW WATER COMPANY groundwater · private · ID7260063 | 459 served |
| COUNTRY SQUIRE ESTATES groundwater · private · ID7260007 | 450 served |
| M AND T WATER AND SEWER DIST groundwater · local government · ID7260026 | 358 served |
| PEPPERWOOD CROSSING/ROCKY MNT UTILITIES groundwater · private · ID7260080 | 336 served |
| JEFFERSON GREENS ESTATES groundwater · private · ID7260075 | 193 served |
Source: U.S. EPA Safe Drinking Water Information System (SDWIS), active community systems, . Look up any system's violations and test results with EPA's search using its ID.
About 101 people were held in Jefferson County's jail, in Vera's latest figure (2019), or 553 per 100,000 residents ages 15–64. In 2014 it was about 56.
Source: Vera Institute of Justice, Incarceration Trends (built from federal Bureau of Justice Statistics jail surveys). Counties without their own jail, or that share one, may show no figure.
2 school districts have their office in Jefferson County. School taxes are usually the largest part of a property tax bill.
Spent $56.7 million — $54.5 million to run schools, about $8,045 per student, plus $238,000 on buildings and equipment. Money in: $12.9 million local (mostly property tax), $48 million state, $6.1 million federal. Long-term debt: $46.7 million.
Spent $7 million — $6.9 million to run schools, about $9,423 per student, plus $89,000 on buildings and equipment. Money in: $982,000 local (mostly property tax), $5.4 million state, $1.3 million federal. Long-term debt: $165,000.
Source: U.S. Census Bureau, 2023 Annual Survey of School System Finances. Districts are listed by the county of their main office; some serve neighboring counties too.
Source: County Health Rankings & Roadmaps 2025 (University of Wisconsin Population Health Institute), which gathers federal data (CDC, Census, and others); measures cover different recent years. Blank lines aren't reported for small counties.
Overall risk: Very Low compared with other U.S. counties. FEMA estimates natural hazards cost Jefferson County about $17.2 million a year on average in buildings, crops and lives. Ability to bounce back (community resilience): Relatively Low; social vulnerability: Very Low.
Source: FEMA National Risk Index (December 2025), expected annual loss. Ratings compare counties nationwide; they're estimates, not predictions.
125 bridges in Jefferson County: 24 in good condition, 97 fair, and 4 poor (3.2%). “Poor” means a main part — the deck, the beams, or the supports — is rated 4 or lower on the federal 0–9 scale. It doesn't mean unsafe to drive; unsafe bridges are closed.
| N 4400 E (SHELTON) over BURGESS CANAL · built 1969 | 510 vehicles a day |
| E 700 N RD over BUTTE MARKET LAKE CANAL · built 1962 | 61 vehicles a day |
| E 421 N over LEWISVILLE CANAL · built 1960 | 50 vehicles a day |
| 2350 NORTH over CAMAS CREEK · built 1972 | 20 vehicles a day |
Source: Federal Highway Administration, National Bridge Inventory (2025 submission). Includes state, county and city bridges.
Federal grants paid for $3.6 million of work in Jefferson County in fiscal 2025, about $118 per resident — to the county, cities, schools, hospitals, nonprofits and others.
Source: USAspending.gov, grants by place of performance, fiscal 2025 (Oct. 2024 to Sept. 2025). Search it by county to see each award.
From Grants.gov: posted grants listing county governments as eligible, soonest deadline first; research-only and overseas programs left out; list updated 2026-10-13, refreshed weekly. 62 are open in all. Cities, towns, school districts and nonprofits have their own lists there.
Registration deadlines, early voting and polling places for Idaho are on the federal site vote.gov, which links to the state's official election office.
The budget, property tax rates, audits, local officials and offices for Jefferson County come from the county's own records, which we haven't gathered — not gathered, never hidden. See what a full county site looks like, or ask to have Jefferson County built: brayden.ozark@gmail.com.
More of Idaho: the state government and every county in Idaho.
Nearby counties: Madison County (33 mi) · Clark County (34 mi) · Bingham County (40 mi) · Butte County (43 mi) · Bonneville County (44 mi) · Fremont County (51 mi).