Fremont County is a county in Idaho, United States, in the state’s eastern corner along the Montana and Wyoming lines, with a slice of Yellowstone National Park reaching into its northeast edge. It had a population of 13,388 at the 2020 census and covers 1,896 square miles (4,910 km2) — 1,864 square miles land, 32 square miles water — centred near 44°13′N 111°29′W.
St. Anthony is the county seat, and its postal code is 83445. The county has 8 incorporated cities and several unincorporated communities. It sits in the Mountain time zone and was organized in 1893.
Towns & Villages in Fremont County
Fremont County has eight incorporated cities and a scatter of unincorporated communities strung along U.S. Route 20 and the Teton and Henrys Fork river valleys. CDP = census-designated place; Unincorp. = unincorporated community with no municipal government.
| Place | Type | Pop. | ZIP |
|---|---|---|---|
| St. Anthony | City · seat | 3,606 | 83445 |
| Ashton | City | 949 | 83420 |
| Island Park | City | — | 83429 |
| Newdale | City | — | 83436 |
| Parker | City | — | 83438 |
| Teton | City | — | 83451 |
| Drummond | City | — | — |
| Warm River | City | — | — |
| Chester | Unincorp. | — | 83421 |
| Egin | Unincorp. | — | — |
| Squirrel | Unincorp. | — | — |
| Macks Inn | Unincorp. | — | 83433 |
| Last Chance | Unincorp. | — | — |
Macks Inn and Last Chance are resort communities inside Island Park’s city limits, on the Henrys Fork near the Yellowstone gateway; both are listed here because the old post named them and they carry their own long-standing local identity even though they fall within Island Park proper.
ZIP Codes
- 83445 — St. Anthony
- 83420 — Ashton
- 83451 — Teton
- 83436 — Newdale
- 83429 — Island Park (also serves Last Chance)
- 83438 — Parker (PO Box)
- 83421 — Chester (PO Box)
- 83433 — Macks Inn (PO Box)
Drummond, Warm River, Egin, and Squirrel have no separate ZIP code and are served by a neighboring post office.
Geography
Fremont County lies on the upper Snake River Plain where it meets the Yellowstone Plateau, ranging from irrigated farmland along the Henrys Fork and Teton River to forested highlands abutting the Continental Divide. The Henrys Fork of the Snake River and the Teton River are the county’s principal waterways, and Island Park Reservoir sits in the county’s northwest.
The county borders Jefferson County to the south and Madison County to the southeast in Idaho, Clark County to the west, and Teton County, Idaho to the southeast across the Teton Range foothills. Across the state line it borders Wyoming’s Teton County to the east and Montana’s Gallatin County to the north.
Demographics
Fremont County had 13,388 residents at the 2020 census. St. Anthony (3,606) and Ashton (949) are its two largest communities. Median household income runs below the Idaho median of $74,942, typical of the county’s farming and ranching economic base. Population density is about 7 people per square mile.
Economy & Local Life
Agriculture anchors the local economy — seed potatoes, barley, and wheat are the county’s major crops, irrigated from the Henrys Fork and Teton systems. The Idaho Department of Correction operates a work camp in the county, and tourism tied to Island Park, Mesa Falls, and the Yellowstone/Teton gateway draws seasonal visitors and snowmobile traffic in winter. Madison Memorial Hospital in neighboring Rexburg serves as the area’s nearest trauma center.
History
Fremont County was organized on March 4, 1893, from part of Bingham County, and named for John C. Frémont, the 19th-century explorer and army officer who led survey expeditions through the northern Rockies. St. Anthony was platted as a Mormon settlement along the Henrys Fork in the 1880s and became the county seat at organization. The Teton Dam disaster of 1976, which flooded parts of the Snake River Plain downstream, originated on the Teton River near the county’s southern edge.
Getting There
- Rexburg, Idaho — 18 miles south
- Idaho Falls, Idaho — 38 miles south
- West Yellowstone, Montana — 30 miles northeast
- Jackson, Wyoming — 60 miles southeast
U.S. Route 20 runs the length of the county, linking St. Anthony and Ashton to Idaho Falls in the south and West Yellowstone in the north. Idaho Falls Regional Airport is the nearest commercial airport.
Frequently Asked Questions
Where is Fremont County, Idaho?
It is in Idaho’s eastern corner, bordering Wyoming and Montana, with part of Yellowstone National Park inside its boundary.
What is the population of Fremont County?
13,388 at the 2020 census.
How big is Fremont County?
1,896 square miles (4,910 km2), of which 32 square miles is water.
What is the county seat of Fremont County?
St. Anthony is the county seat and largest city.
How many towns are in Fremont County?
Eight incorporated cities plus several unincorporated communities such as Chester, Macks Inn, and Last Chance.
What ZIP codes are in Fremont County?
Eight ZIP codes, led by 83445 (St. Anthony) and 83420 (Ashton).
Is Yellowstone National Park in Fremont County?
A small section of Yellowstone’s southwest corner extends into the county’s northeast.
More counties in this state: Towns and villages in Idaho.