Idaho Counties. List Alphabetically (and by Population)
How many counties are there in Idaho? As of 2024, there are a total of 44 counties in the state of Idaho. Among them, Owyhee County is the oldest one (established in 1863) while Caribou County is the youngest (established in 1919). With population of 392,365, Ada County is the most populated. The biggest county by land area is Idaho County (21,976 km²) and the smallest is Payette County (1,057 km²).
Largest Counties in Idaho
1. Idaho County
County Seat: Grangeville
- Area: 8,503 square miles
- Population: Approximately 16,541 (2020 census)
- Area Codes: 208, 986
- Latitude: 45.9269° N
- Longitude: 116.1222° W
Location and History
Idaho County, the largest county in Idaho by area, is located in the north-central part of the state. Established in 1864 during the Idaho Territory period, it was one of the original counties and played a significant role during the Gold Rush era. Grangeville, the county seat, emerged as a key town during this time and remains the cultural and economic hub of the county. The county’s vast landscape includes part of the Nez Perce National Historical Park, which commemorates the history of the Nez Perce tribe and their resistance to displacement. Idaho County’s economy has traditionally been based on timber, agriculture, and mining, though tourism and outdoor recreation have become increasingly important.
Major Highways and Landmarks
Idaho County is traversed by U.S. Route 95, the primary north-south route through the county, connecting it to Lewiston and Boise. The county is home to several major landmarks, including the Frank Church-River of No Return Wilderness, the largest contiguous wilderness area in the lower 48 states, offering opportunities for hiking, fishing, and rafting. The Salmon River, also known as “The River of No Return,” runs through the county and is famous for its whitewater rafting and fishing. The Camas Prairie Centennial Marsh Wildlife Management Area, near Grangeville, is another notable location, known for its seasonal wildflower blooms and birdwatching.
2. Owyhee County
County Seat: Murphy
- Area: 7,666 square miles
- Population: Approximately 12,133 (2020 census)
- Area Codes: 208, 986
- Latitude: 42.5241° N
- Longitude: 116.6145° W
Location and History
Owyhee County is located in southwestern Idaho, bordering Nevada and Oregon. It was established in 1863 and is named after a group of Hawaiian fur trappers who disappeared in the area in the early 19th century— “Owyhee” being an older spelling of “Hawaii.” The county seat, Murphy, is a small, unincorporated community that serves as the administrative center of this vast and sparsely populated county. Owyhee County is characterized by its rugged landscapes, including vast deserts, canyons, and the Owyhee Mountains, making it a destination for outdoor enthusiasts. The county’s economy has traditionally been based on ranching and mining, with agriculture playing a significant role.
Major Highways and Landmarks
Owyhee County is accessible via State Highways 51 and 78, which connect the county to Boise and other parts of Idaho. Significant landmarks include the Owyhee Canyonlands, a remote and scenic area known for its deep canyons, wild rivers, and unique rock formations. The Bruneau Dunes State Park, home to the tallest single-structured sand dune in North America, is another major attraction, offering opportunities for sandboarding, hiking, and stargazing. The Silver City Historic District, a well-preserved ghost town from the mining boom of the late 19th century, provides a glimpse into the county’s rich history.
3. Custer County
County Seat: Challis
- Area: 4,937 square miles
- Population: Approximately 4,275 (2020 census)
- Area Codes: 208, 986
- Latitude: 44.5042° N
- Longitude: 114.2262° W
Location and History
Custer County is located in central Idaho and was established in 1881, named after General George Armstrong Custer. The county is known for its rugged terrain, which includes the Sawtooth, Lost River, and White Cloud mountain ranges. Challis, the county seat, developed as a mining town during Idaho’s gold rush in the late 19th century and remains the cultural and economic center of the county. The area’s history is deeply tied to mining, with several ghost towns like Bayhorse providing a glimpse into the county’s past. Today, Custer County is known for its outdoor recreation opportunities, particularly in the Salmon-Challis National Forest.
Major Highways and Landmarks
Custer County is traversed by U.S. Route 93, which runs north-south through the county, providing access to Salmon to the north and Twin Falls to the south. Major landmarks include the Sawtooth National Recreation Area, which offers world-class hiking, camping, and fishing in one of the most scenic areas of Idaho. Borah Peak, the highest point in Idaho, is located in the Lost River Range and is a popular destination for climbers. The Yankee Fork Gold Dredge, a remnant of the county’s mining past, is now a historic site and museum. The Land of the Yankee Fork State Park, near Challis, preserves the history of Idaho’s gold rush era and offers a glimpse into the lives of the miners who once populated the area.
4. Elmore County
County Seat: Mountain Home
- Area: 3,101 square miles
- Population: Approximately 29,130 (2020 census)
- Area Codes: 208, 986
- Latitude: 43.1327° N
- Longitude: 115.6912° W
Location and History
Elmore County is located in southwestern Idaho, with Mountain Home as its county seat. Established in 1889, the county was named after the Ida Elmore Mines, one of the state’s most productive gold mines during the 19th century. Mountain Home, initially a small stagecoach station, grew significantly with the establishment of Mountain Home Air Force Base during World War II, which continues to be a major employer in the area. Elmore County’s economy has traditionally been based on agriculture and ranching, with tourism and military-related activities playing significant roles today.
Major Highways and Landmarks
Elmore County is served by Interstate 84, which runs through Mountain Home and connects the county to Boise and other major cities. U.S. Route 20 also crosses the county, providing access to the Craters of the Moon National Monument to the east. Key landmarks include the Bruneau Dunes State Park, known for its impressive sand dunes and observatory, and the Anderson Ranch Reservoir, a popular spot for boating, fishing, and camping. The county is also home to parts of the Boise National Forest, offering extensive opportunities for hiking, hunting, and wildlife observation. The Snake River Birds of Prey National Conservation Area, located in the southwestern part of the county, is one of the most important raptor habitats in North America.
5. Lemhi County
County Seat: Salmon
- Area: 4,569 square miles
- Population: Approximately 8,074 (2020 census)
- Area Codes: 208, 986
- Latitude: 45.1751° N
- Longitude: 113.8925° W
Location and History
Lemhi County is located in eastern Idaho, bordering Montana to the north. It was established in 1869 and named after Fort Lemhi, a Mormon mission to the Shoshone Indians. The county seat, Salmon, is named after the Salmon River, which runs through the county and is known as “The River of No Return” due to its challenging rapids and remote wilderness. Lemhi County’s history is closely tied to exploration, mining, and the Native American tribes that have lived in the region for centuries. The county is also known as the birthplace of Sacagawea, the Shoshone woman who played a crucial role in the Lewis and Clark Expedition.
Major Highways and Landmarks
Lemhi County is traversed by U.S. Route 93, which runs north-south through the county, connecting it to Missoula, Montana, to the north and Twin Falls, Idaho, to the south. Major landmarks include the Sacajawea Interpretive, Cultural, and Education Center in Salmon, which honors the life and legacy of Sacagawea. The Lemhi Pass, a historic site on the Continental Divide, is where Lewis and Clark first crossed into Idaho during their expedition. The Salmon-Challis National Forest, encompassing much of the county, offers extensive opportunities for hiking, camping, and fishing, with the Middle Fork of the Salmon River being particularly popular for whitewater rafting. The Lost Trail Pass Ski Area, located on the Idaho-Montana border, is another notable recreational destination.
6. Twin Falls County
County Seat: Twin Falls
- Area: 1,928 square miles
- Population: Approximately 90,046 (2020 census)
- Area Codes: 208, 986
- Latitude: 42.5629° N
- Longitude: 114.4609° W
Location and History
Twin Falls County is located in southern Idaho and was established in 1907. The county was named after the Twin Falls, a pair of waterfalls on the Snake River. The city of Twin Falls, the county seat, grew rapidly in the early 20th century with the construction of irrigation projects that transformed the arid region into fertile farmland. Today, Twin Falls County is a major agricultural hub, known for its dairy production, potatoes, and sugar beets. The county’s economy has diversified in recent years, with tourism and manufacturing also playing significant roles.
Major Highways and Landmarks
Twin Falls County is served by Interstate 84, which runs along the northern edge of the county, and U.S. Route 93, which provides access to Nevada to the south. Key landmarks include Shoshone Falls, often called the “Niagara of the West,” which is actually higher than Niagara Falls and is a major tourist attraction. The Perrine Bridge, which spans the Snake River Canyon, is a popular spot for BASE jumping and offers stunning views of the canyon. The county is also home to the Hagerman Fossil Beds National Monument, which contains one of the richest fossil deposits in North America. The College of Southern Idaho, located in Twin Falls, is a significant educational and cultural institution in the region.
7. Blaine County
County Seat: Hailey
- Area: 2,661 square miles
- Population: Approximately 24,272 (2020 census)
- Area Codes: 208, 986
- Latitude: 43.5196° N
- Longitude: 114.3153° W
Location and History
Blaine County is located in central Idaho and was established in 1895. The county was named after James G. Blaine, a prominent American statesman. Hailey, the county seat, developed as a mining town in the late 19th century but is now known for its proximity to the Sun Valley Resort, a world-famous ski destination. Blaine County’s economy is heavily influenced by tourism, with Sun Valley and the nearby town of Ketchum serving as major hubs for outdoor recreation, arts, and culture. The area is also known for its scenic beauty, with the Sawtooth Mountains and the Big Wood River providing stunning backdrops for various activities.
Major Highways and Landmarks
Blaine County is accessible via State Highway 75, also known as the Sawtooth Scenic Byway, which runs north-south through the county, connecting Hailey and Ketchum to the rest of the state. Major landmarks include the Sun Valley Resort, which offers world-class skiing, hiking, and cultural events, and the Sawtooth National Recreation Area, known for its rugged mountains, alpine lakes, and extensive trail systems. The Hemingway Memorial, located near Sun Valley, commemorates the famous author who spent much of his later life in the area. The county is also home to the Craters of the Moon National Monument and Preserve, a unique volcanic landscape that offers a stark contrast to the surrounding mountains.
8. Bonneville County
County Seat: Idaho Falls
- Area: 1,901 square miles
- Population: Approximately 119,062 (2020 census)
- Area Codes: 208, 986
- Latitude: 43.4917° N
- Longitude: 112.0339° W
Location and History
Bonneville County is located in eastern Idaho, with Idaho Falls as its county seat. Established in 1911, the county was named after Benjamin Bonneville, a French-born explorer who mapped much of the American West in the early 19th century. Idaho Falls, originally known as Eagle Rock, developed as a railroad hub and agricultural center. Today, it is the largest city in eastern Idaho and a key economic and cultural center for the region. The county’s economy is diverse, with significant contributions from agriculture, manufacturing, healthcare, and energy, particularly due to the Idaho National Laboratory, a major nuclear research facility.
Major Highways and Landmarks
Bonneville County is served by U.S. Route 26, which runs through Idaho Falls and connects the county to Jackson, Wyoming, and Interstate 15, which provides north-south access through the region. Major landmarks include the Idaho Falls River Walk, a scenic path along the Snake River that features beautiful views of the river and the falls. The Tautphaus Park Zoo, one of the oldest zoos in the state, is a popular family destination. The county is also a gateway to Yellowstone and Grand Teton National Parks, with many visitors passing through on their way to these iconic natural wonders. The Museum of Idaho, located in Idaho Falls, offers exhibits on the region’s history, science, and culture.
9. Cassia County
County Seat: Burley
- Area: 2,580 square miles
- Population: Approximately 24,655 (2020 census)
- Area Codes: 208, 986
- Latitude: 42.5356° N
- Longitude: 113.7924° W
Location and History
Cassia County is located in southern Idaho and was established in 1879. The county was named after the Cassia Creek, which runs through the area. Burley, the county seat, developed as a key agricultural center in the early 20th century, particularly with the construction of irrigation canals that transformed the arid landscape into fertile farmland. The county’s economy remains heavily dependent on agriculture, with crops such as potatoes, sugar beets, and barley being significant. In recent years, manufacturing and food processing have also become important industries in the county.
Major Highways and Landmarks
Cassia County is traversed by Interstate 84, which provides access to Boise to the west and Salt Lake City, Utah, to the south. U.S. Route 30 also runs through the county, providing east-west access. Significant landmarks include the City of Rocks National Reserve, a popular destination for rock climbing, hiking, and camping, known for its unique rock formations and historical significance as a landmark on the California Trail. The county is also home to Lake Walcott State Park, offering opportunities for boating, fishing, and birdwatching. The Minidoka National Historic Site, located near Burley, preserves the history of a World War II-era Japanese-American internment camp.
10. Bingham County
County Seat: Blackfoot
- Area: 2,120 square miles
- Population: Approximately 46,236 (2020 census)
- Area Codes: 208, 986
- Latitude: 43.1905° N
- Longitude: 112.3430° W
Location and History
Bingham County is located in eastern Idaho and was established in 1885. The county was named after Henry H. Bingham, a congressman from Pennsylvania. Blackfoot, the county seat, is known as the “Potato Capital of the World” due to its significant role in Idaho’s potato industry. The county’s economy is largely based on agriculture, particularly potatoes, but also includes grains, sugar beets, and livestock. Bingham County’s history is closely tied to the development of irrigation systems, which transformed the Snake River Plain into one of the most productive agricultural regions in the country.
Major Highways and Landmarks
Bingham County is served by Interstate 15, which runs north-south through the county, providing access to Idaho Falls to the north and Pocatello to the south. U.S. Route 26 also crosses the county, providing east-west access. Key landmarks include the Idaho Potato Museum in Blackfoot, which celebrates the history and significance of the potato industry in Idaho. The Fort Hall Indian Reservation, home to the Shoshone-Bannock Tribes, is located in the southeastern part of the county and offers cultural experiences and events. The Snake River, which flows through the county, provides opportunities for fishing, boating, and wildlife observation.
List of All Counties in Idaho Alphabetically
Below please see all Idaho counties which are listed in alphabetical order.
- Ada County, ID
- Adams County, ID
- Bannock County, ID
- Bear Lake County, ID
- Benewah County, ID
- Bingham County, ID
- Blaine County, ID
- Boise County, ID
- Bonner County, ID
- Bonneville County, ID
- Boundary County, ID
- Butte County, ID
- Camas County, ID
- Canyon County, ID
- Caribou County, ID
- Cassia County, ID
- Clark County, ID
- Clearwater County, ID
- Custer County, ID
- Elmore County, ID
- Franklin County, ID
- Fremont County, ID
- Gem County, ID
- Gooding County, ID
- Idaho County, ID
- Jefferson County, ID
- Jerome County, ID
- Kootenai County, ID
- Latah County, ID
- Lemhi County, ID
- Lewis County, ID
- Lincoln County, ID
- Madison County, ID
- Minidoka County, ID
- Nez Perce County, ID
- Oneida County, ID
- Owyhee County, ID
- Payette County, ID
- Power County, ID
- Shoshone County, ID
- Teton County, ID
- Twin Falls County, ID
- Valley County, ID
- Washington County, ID
Map of Idaho Counties
