Twin Falls County is a county in the south central part of the U.S. state of Idaho. As of the 2020 census, the population was 90,046, making it the fifth-most populous county in Idaho. The county seat and largest city is Twin Falls. Twin Falls County is part of the Twin Falls, ID Twin Falls Metropolitan Statistical Area.
Prior to the 1860s, the Twin Falls County area was an unorganized part of Shoshone lands, then as part of the Oregon Country. The area was first organized as part of the original Owyhee County in 1864 as part of Idaho Territory. In 1879 it was partitioned away from Owyhee County to form part of Cassia County. The county is named for a split waterfall on the Snake River of the same name. The Snake River is the county's northern boundary.
Even after Idaho became a state in 1890, the Twin Falls area was very sparsely populated and without significant settlements. That changed after the city of Twin Falls was founded in 1904, and Milner Dam was completed in 1905. Most of the county's other towns were established during this period as well. In response to local government needs for these new communities, which were as much as away from Cassia County's seat at Albion, Twin Falls County was created by the Idaho Legislature on February 21, 1907.
Geography
According to the United States Census Bureau, the county has a total area of , of which is land and (0.4%) is water.
Adjacent counties
- Gooding County - north
- Jerome County - northeast
- Cassia County - east
- Elko County, Nevada - south/Pacific Time Border
- Owyhee County - west
- Elmore County - northwest
Major highways
- 25px US 30
- 25px US 93
- 25px SH-50
- 25px SH-74
National protected areas
- Hagerman Fossil Beds National Monument
- Sawtooth National Forest (part)