Originally part of Oregon Country and then Washington Territory, Idaho became a state in 1890. It’s known for its natural beauty and mining history. Idaho has 44 counties.
10 Largest Counties in Idaho
1. Ada County
County Facts
- Population: 494,967 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83616-83799
- County Seat: Boise
Geography and History
Ada County, located in southwestern Idaho, covers 1,060 square miles. It is situated in the Treasure Valley along the Boise River, with a landscape that includes desert plains, rivers, and foothills. Established in 1864, Ada County was named after Ada Riggs, the daughter of one of the founders of Boise. The county’s economy initially revolved around agriculture and mining, but with the growth of Boise, it has become a major hub for technology, manufacturing, and education. The area’s relatively mild climate and natural beauty have contributed to its rapid population growth, making it the most populous county in Idaho. Boise, the state capital, is also the economic and cultural heart of the county.
Colleges and Universities
- Boise State University: A public research university known for its engineering, business, and computer science programs, as well as its iconic blue football field.
- College of Western Idaho: A community college offering associate degrees and vocational training in fields such as health care, business, and technology.
- Concordia University School of Law (Boise Campus): A private law school that offers legal education with a focus on community service and public interest law.
Major Landmarks
Ada County is home to landmarks such as The Idaho State Capitol, a historic building located in downtown Boise. Boise River Greenbelt is a scenic 25-mile path along the river that provides outdoor recreation opportunities. Julia Davis Park is home to the Boise Art Museum, the Idaho Historical Museum, and the Zoo Boise. Bogus Basin Mountain Recreation Area offers skiing and mountain activities. The Old Idaho Penitentiary, now a museum, provides insights into the state’s prison history. The Boise Depot is a historic train station offering views of the city and the foothills.
2. Canyon County
County Facts
- Population: 231,105 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83605-83686
- County Seat: Caldwell
Geography and History
Canyon County is located in southwestern Idaho, adjacent to Ada County, covering 604 square miles. The county features fertile plains, fed by the Boise River, making it a major agricultural area. Established in 1892, the county’s name reflects the Snake River Canyon that forms its western boundary. Historically, the area was settled as an agricultural region, with irrigation playing a significant role in its development. The county is part of the larger Treasure Valley, which includes urban, suburban, and rural communities. Over time, the county’s economy has diversified, with manufacturing and retail becoming key contributors alongside agriculture.
Colleges and Universities
- College of Idaho: A private liberal arts college in Caldwell, known for its strong programs in biology, business, and education.
- Treasure Valley Community College (Caldwell Campus): Offers vocational programs, associate degrees, and community education in various fields.
- Northwest Nazarene University (nearby in Nampa): A private Christian liberal arts university offering undergraduate and graduate degrees in arts, sciences, and business.
Major Landmarks
Canyon County is known for Lake Lowell, a popular spot for boating, fishing, and wildlife viewing. Deer Flat National Wildlife Refuge surrounds the lake and provides habitat for migratory birds. Farms and vineyards are a key feature of the region, and Ste. Chapelle Winery offers tours and tastings. Caldwell’s Indian Creek Plaza hosts events year-round, including the famous Winter Wonderland Festival. Warhawk Air Museum in Nampa displays military aircraft and history exhibits. The Canyon County Fair is an annual event that celebrates the area’s agricultural heritage.
3. Kootenai County
County Facts
- Population: 171,362 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83814-83877
- County Seat: Coeur d’Alene
Geography and History
Kootenai County is located in northern Idaho and covers 1,316 square miles, featuring a diverse landscape of lakes, rivers, and mountains. It was established in 1864 and named after the Kootenai tribe, one of the region’s Native American groups. The area was initially settled during the gold rush in the 1860s and later developed into a logging and mining hub. Today, Kootenai County is known for its tourism and outdoor recreation, driven by attractions like Lake Coeur d’Alene. Coeur d’Alene has grown into a regional center for business, health care, and tourism, drawing visitors for its natural beauty and recreational opportunities.
Colleges and Universities
- North Idaho College: A public community college in Coeur d’Alene offering associate degrees, technical certifications, and transfer programs to four-year universities.
- University of Idaho (Coeur d’Alene Center): A satellite campus offering undergraduate and graduate programs in business, education, and engineering.
- Lewis-Clark State College (Coeur d’Alene): Provides bachelor’s degree programs in nursing, business, and teacher education.
Major Landmarks
Kootenai County’s most famous landmark is Lake Coeur d’Alene, which offers boating, fishing, and hiking opportunities. Tubbs Hill, located near downtown Coeur d’Alene, provides scenic trails along the lake. The Coeur d’Alene Resort is a luxury hotel with a world-renowned golf course featuring a floating green. Silverwood Theme Park, the largest theme park in the Pacific Northwest, offers roller coasters and water attractions. Farragut State Park, a former naval training base, is a popular spot for camping and hiking. The Trail of the Coeur d’Alenes, a 73-mile paved bike path, traverses the county’s stunning natural landscape.
4. Bonneville County
County Facts
- Population: 123,964 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83401-83406
- County Seat: Idaho Falls
Geography and History
Bonneville County is located in eastern Idaho and spans 1,901 square miles, featuring a mix of plains, rivers, and mountains. The county was established in 1911 and named after Benjamin Bonneville, an explorer of the American West. Idaho Falls, the county seat, grew as a hub for agriculture and commerce, thanks to its location along the Snake River. The development of hydroelectric power and irrigation systems transformed the area into a fertile agricultural region. Bonneville County is also known for its proximity to Yellowstone and Grand Teton National Parks, attracting tourists and outdoor enthusiasts.
Colleges and Universities
- Idaho State University (Idaho Falls Campus): Offers undergraduate and graduate programs in business, health sciences, and education.
- College of Eastern Idaho: A public community college offering associate degrees, vocational training, and transfer programs.
- University of Idaho (Idaho Falls Research and Extension Center): Provides research opportunities and advanced degree programs, particularly in energy and engineering.
Major Landmarks
Bonneville County’s landmarks include the Idaho Falls River Walk, a scenic path that follows the Snake River and passes by the city’s iconic waterfalls. The Museum of Idaho offers exhibits on local history, science, and culture. Tautphaus Park Zoo is home to a variety of animals and educational programs. Heise Hot Springs offers natural hot pools and camping, while Palisades Reservoir, located nearby, is a popular destination for boating, fishing, and camping. Sandy Downs is the venue for horse races, rodeos, and other events throughout the year.
5. Bannock County
County Facts
- Population: 87,018 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83201-83221
- County Seat: Pocatello
Geography and History
Bannock County is located in southeastern Idaho and covers 1,147 square miles. It is named after the Bannock Native American tribe, who originally inhabited the area. Established in 1893, Bannock County became a transportation hub with the construction of the Oregon Short Line Railroad, which ran through Pocatello. The city quickly grew as a center for trade and industry. The county’s geography includes high desert plains and mountains, offering a variety of outdoor activities. Today, Bannock County’s economy is diversified, with sectors like education, health care, and manufacturing contributing to its growth.
Colleges and Universities
- Idaho State University: A major public research university located in Pocatello, offering programs in health sciences, engineering, business, and more.
- College of Eastern Idaho (Satellite Programs): Provides vocational and technical education to residents of Bannock County through partnerships with local schools and institutions.
Major Landmarks
Bannock County is home to the Fort Hall Replica, a reconstruction of the historic trading post that was central to early pioneers and traders. Pocatello Zoo offers exhibits featuring animals native to the region. L.E. and Thelma E. Stephens Performing Arts Center is a venue for concerts, theater, and cultural events. The nearby Pebble Creek Ski Area is a popular winter sports destination, while Ross Park features a pool, water slides, and picnic areas. The Bannock County Historical Museum offers exhibits on local history, including Native American heritage and the region’s early settlers.
6. Twin Falls County
County Facts
- Population: 90,046 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83301-83344
- County Seat: Twin Falls
Geography and History
Twin Falls County, located in southern Idaho, covers 1,928 square miles and is known for its fertile farmland, thanks to the Snake River and an extensive irrigation system. Established in 1907, the county is named after the Twin Falls waterfalls on the Snake River. The region’s economy has long been based on agriculture, particularly dairy farming, which remains a key industry today. In recent years, Twin Falls County has diversified, with manufacturing, technology, and food processing becoming important contributors. The area’s natural beauty and outdoor recreational opportunities make it a popular destination for both residents and visitors.
Colleges and Universities
- College of Southern Idaho: A public community college in Twin Falls, offering associate degrees, technical certifications, and transfer programs in fields like health care, agriculture, and technology.
- University of Idaho (Twin Falls Extension): Provides research and extension services in agriculture, along with degree programs in collaboration with local institutions.
Major Landmarks
Twin Falls County is home to the dramatic Shoshone Falls, known as the “Niagara of the West,” which is higher than Niagara Falls and located on the Snake River. The Perrine Bridge offers stunning views of the Snake River Canyon and is a popular spot for BASE jumping. Sawtooth National Forest provides hiking, camping, and outdoor adventures. Dierkes Lake Park offers swimming, fishing, and hiking trails. The Herrett Center for Arts and Science at the College of Southern Idaho features a planetarium and museum exhibits. Thousand Springs State Park, located nearby, showcases waterfalls, springs, and scenic views.
7. Bingham County
County Facts
- Population: 47,992 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83210-83221
- County Seat: Blackfoot
Geography and History
Bingham County is located in eastern Idaho and spans 2,120 square miles. It was named after Henry H. Bingham, a congressman from Pennsylvania. Established in 1885, the county’s economy was initially based on agriculture, particularly potato farming, which remains a major industry today. The region’s fertile soil and irrigation from the Snake River make it ideal for farming. The county is also known for its Native American heritage, as it includes part of the Fort Hall Indian Reservation, home to the Shoshone-Bannock Tribes.
Colleges and Universities
- Idaho State University (Satellite Campus in Blackfoot): Provides educational and vocational programs for residents of Bingham County.
- College of Eastern Idaho (Partnership Programs): Offers career training and technical education in collaboration with local schools.
Major Landmarks
Bingham County is home to the Idaho Potato Museum in Blackfoot, which celebrates the county’s role as a leading potato producer in the U.S. Fort Hall Indian Reservation offers cultural experiences and events that highlight the traditions of the Shoshone-Bannock Tribes. The Fort Hall Replica and Museum provides historical insights into the region’s early trading history. Massacre Rocks State Park, located nearby, features hiking trails and views of the Snake River. Tilden Bridge is a popular fishing and boating destination.
8. Nez Perce County
County Facts
- Population: 42,090 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83501-83544
- County Seat: Lewiston
Geography and History
Nez Perce County is located in north-central Idaho and spans 856 square miles. It was named after the Nez Perce Native American tribe, who historically inhabited the region. Established in 1864, the county’s economy initially revolved around fur trading and gold mining, with Lewiston serving as an important port and supply center along the Clearwater River. The county’s rich agricultural land and access to the river have supported industries such as wheat farming, timber, and paper production. Today, Nez Perce County continues to be a key player in agriculture and shipping, thanks to the Port of Lewiston, Idaho’s only seaport.
Colleges and Universities
- Lewis-Clark State College: A public college in Lewiston offering bachelor’s degrees in nursing, education, and business.
- University of Idaho (Lewiston Outreach Center): Provides continuing education and degree programs in partnership with local institutions.
Major Landmarks
Nez Perce County’s landmarks include Hells Canyon, the deepest river gorge in North America, which offers whitewater rafting, hiking, and wildlife viewing. Nez Perce National Historical Park preserves sites important to the history and culture of the Nez Perce people. The Clearwater River is popular for fishing and boating, while the Snake River is central to Lewiston’s role as Idaho’s only seaport. The Lewis-Clark Center for Arts & History in Lewiston showcases local history and art. Lewiston Hill provides panoramic views of the valley, and Hells Gate State Park offers outdoor recreation along the river.
9. Latah County
County Facts
- Population: 40,385 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83501-83872
- County Seat: Moscow
Geography and History
Latah County is located in northern Idaho, covering 1,077 square miles. The county was created in 1888 from parts of Nez Perce County and was the first county established by the Idaho Legislature. It is named after the Nez Perce word “Latah,” meaning the place of pine trees and streams. Moscow, the county seat, grew as a center for agriculture and education, with the University of Idaho playing a central role in the region’s development. Latah County’s geography includes rolling hills known as the Palouse, which are famous for wheat and lentil farming.
Colleges and Universities
- University of Idaho: The state’s flagship public university, located in Moscow, offers programs in law, engineering, agriculture, and the liberal arts.
- Washington State University: Located nearby in Pullman, Washington, but serving many Latah County residents, WSU offers a range of graduate and undergraduate programs.
- North Idaho College (Moscow Outreach Center): Provides educational programs and community courses in partnership with local institutions.
Major Landmarks
Latah County’s landmarks include the University of Idaho Arboretum and Botanical Garden, a beautiful green space featuring native and exotic plants. Moscow Farmers Market is a popular local event that showcases the region’s agricultural products. The Appaloosa Museum celebrates the history of the Appaloosa horse, which has deep roots in Nez Perce culture. Kamiak Butte, located just outside the county, offers hiking trails and stunning views of the Palouse. The Lionel Hampton Jazz Festival, held annually at the University of Idaho, attracts world-class musicians and jazz enthusiasts.
10. Elmore County
County Facts
- Population: 28,666 (2020 Census)
- Area Codes: 208, 986
- ZIP Codes: 83623-83647
- County Seat: Mountain Home
Geography and History
Elmore County, located in southwestern Idaho, spans 3,101 square miles and includes desert, mountains, and rivers. The county was established in 1889 and named after the Ida Elmore Mines, which were major producers of silver and gold. Historically, Elmore County’s economy was driven by mining and ranching, with the development of railroads further boosting growth. Mountain Home, the county seat, became a key supply center during Idaho’s mining boom. Today, Elmore County’s economy includes agriculture, military, and tourism, with Mountain Home Air Force Base playing a significant role in the area.
Colleges and Universities
- College of Western Idaho (Mountain Home): Provides educational opportunities in fields such as business, health sciences, and technical trades.
- Idaho State University (Satellite Programs): Offers educational and vocational training in partnership with local schools and businesses.
Major Landmarks
Elmore County is known for Bruneau Dunes State Park, which features the tallest single-structured sand dune in North America and offers camping, hiking, and stargazing. Anderson Ranch Reservoir is a popular spot for fishing, boating, and water sports. Three Island Crossing State Park, located nearby, commemorates the historic Oregon Trail crossing of the Snake River. Mountain Home Historical Museum provides insights into the county’s pioneer and military history. Castle Rock Reserve and King Hill are popular for hiking and exploring Idaho’s rugged landscapes.