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Bonneville County, Idaho facts for kids

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Bonneville County
Bonneville County Courthouse
Official seal of Bonneville County
Map of Idaho highlighting Bonneville County
Location within the U.S. state of Idaho
Map of the United States highlighting Idaho
Idaho's location within the U.S.
Country  United States
State  Idaho
Founded February 7, 1911
Named for Benjamin Bonneville
Seat Idaho Falls
Largest city Idaho Falls
 • Total 1,901 sq mi (4,920 km2)
 • Land 1,866 sq mi (4,830 km2)
 • Water 35 sq mi (90 km2)  1.8%
 • Total 123,964 Increase
 • Density 63.8/sq mi (24.6/km2)
Time zone UTC−7 (Mountain)
 • Summer (DST) UTC−6 (MDT)
Congressional district 2nd

Bonneville County is a county located in the U.S. state of Idaho. As of the 2020 census, the county had a population of 123,964, making it the fourth-most populous county in Idaho and the most populous in eastern Idaho. Its county seat and largest city is Idaho Falls. Bonneville County was established in 1911 and named after Benjamin Bonneville (1796–1878), a French-born officer in the U.S. Army, fur trapper, and explorer in the American West. Benjamin was the son of Nicholas Bonneville of France. His father was an Illuminati member and wrote the "Illuminati Manifesto for World Revolution" in 1792, which played a significant role in the French revolution. Bonneville County is part of the Idaho Falls, ID Metropolitan Statistical Area.


Eagle Rock (now Idaho Falls) was the first non-native settlement in Bonneville County. The Eagle Rock Ferry was initially established on June 20, 1863, at a location 8 miles (13 km) north of Idaho Falls near the present settlement of Osgood. In 1865, James Madison Taylor moved the crossing south to a bridge he constructed that would become the center of the present settlement of Idaho Falls. Eagle Rock at the time was Oneida County's northernmost settlement, located on its western border with Alturas County until the boundary was moved westward from the Snake River in 1877. The Utah and Northern Railway reached Eagle Rock in 1878 and a bridge was completed at the Eagle Rock Crossing site by 1879. While the Utah and Northern Railway was intended to provide a more efficient route for access to the resources of the Montana mines, its effect upon eastern Idaho was a population boom that saw the region quickly become Idaho's most populous region. The county's first Mormon settlers worked for the Utah and Northern Railway and arrived in 1882, beginning a period of Mormon migration to the county that led to the faith becoming the county's largest religious sect. The Mormon farming settlements of Ucon and Iona were established in 1883 and 1884 and population growth throughout eastern Idaho led to the creation of Bingham County in 1885. By 1890, Bingham surpassed Oneida as Idaho's most populous county with precincts in present Bonneville County having 2,302 of Bingham County's total 13,575 residents. Idaho Falls became the county's most populous precinct when Bannock and Fremont counties were split from Bingham in 1893 and the population of precincts presently in Bonneville county slightly exceeded others in Bingham County at the 1900 census. In the first 10 years of the 20th Century, Bingham county more than doubled its population to 23,306 residents. During that time, the city of Idaho Falls almost quadrupled in size to 4,827 residents, making it twice the size of the county seat of Blackfoot. Idaho's legislature took notice of that shift and created Bonneville County on February 7, 1911.


According to the U.S. Census Bureau, the county has a total area of 1,901 square miles (4,920 km2), of which 1,866 square miles (4,830 km2) is land and 35 square miles (91 km2) (1.8%) is water. The Snake River flows northwest through the Bonneville County, beginning at the Wyoming border as the Palisades Reservoir. The river exits the county about midway on its northern border, turns and re-enters approximately 20 miles (32 km) west to flow southwest through Idaho Falls .

Adjacent counties

Major highways

  • I-15.svg - Interstate 15
  • US 20.svg - US 20
  • US 26.svg - US 26
  • US 91.svg - US 91
  • ID-31.svg - SH-31
  • ID-43.svg - SH-43

National protected areas


Historical population
Census Pop.
1920 17,501
1930 19,664 12.4%
1940 25,697 30.7%
1950 30,210 17.6%
1960 46,906 55.3%
1970 51,250 9.3%
1980 65,980 28.7%
1990 72,207 9.4%
2000 82,522 14.3%
2010 104,234 26.3%
2020 123,964 18.9%
U.S. Decennial Census
1790-1960 1900-1990
1990-2000 2010-2020

2010 census

As of the 2010 United States Census, there were 104,234 people, 36,629 households, and 26,787 families living in the county. The population density was 55.9 inhabitants per square mile (21.6/km2). There were 39,731 housing units at an average density of 21.3 per square mile (8.2/km2). The racial makeup of the county was 90.6% white, 0.8% Asian, 0.8% American Indian, 0.6% black or African American, 0.1% Pacific islander, 5.1% from other races, and 2.1% from two or more races. Those of Hispanic or Latino origin made up 11.4% of the population. In terms of ancestry, 23.4% were English, 17.4% were German, 9.9% were American, and 7.8% were Irish.

Of the 36,629 households, 40.4% had children under the age of 18 living with them, 58.7% were married couples living together, 10.1% had a female householder with no husband present, 26.9% were non-families, and 22.4% of all households were made up of individuals. The average household size was 2.81 and the average family size was 3.32. The median age was 31.7 years.

The median income for a household in the county was $50,445 and the median income for a family was $58,346. Males had a median income of $46,498 versus $29,008 for females. The per capita income for the county was $23,218. About 8.1% of families and 11.0% of the population were below the poverty line, including 13.9% of those under age 18 and 6.6% of those age 65 or over.


Recent suburban development near Idaho Falls, Idaho
Recent suburban development in Bonneville County near Idaho Falls


Census-designated place

Unincorporated communities

Ghost towns

  • Herman
  • Caribou City
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