Map
|- class="hiddenStructure"
| colspan="2" style="text-align: center;" |
Location in the state of
|-
| colspan="2" style="text-align: center; background:#E0E0E0;" | Statistics
|-
!style="background:#efefef;"| Formed
|
|-
!style="background:#efefef;"| Seat
|
|-
!style="background:#efefef;"| License plate
|
|-
!style="background:#efefef;"| Area - Total - Land - Water
|
Most of the county's population lives in Malad City and the surrounding Malad Valley. The county is named for Oneida Lake, New York, the area from which most of the early settlers had emigrated.
Oneida County was organized on January 22, 1864 as part of Idaho Territory. The original county seat was at Soda Springs in present-day Caribou County. The county seat was moved to Malad City in 1866 because of its population growth and location on the freight road and stagecoach line between Corinne, Utah, and the mines in Butte, Montana.
According to the U.S. Census Bureau, the county has a total area of 3,112 km² (1,202 mi²). 3,109 km² (1,200 mi²) of it is land and 3 km² (1 mi²) of it (0.11%) is water.
Elkhorn Peak is the highest point in the county, at 9,095 feet. Alternating valleys and ridges of mountains or hills typify the topography. Grassland and sagebrush cover most areas. The Curlew National Grassland lies within the county.
As of the census2 of 2000, there were 4,125 people, 1,430 households, and 1,092 families residing in the county. The population density was 1/km² (3/mi²). There were 1,755 housing units at an average density of 1/km² (2/mi²). The racial makeup of the county was 97.50% White, 0.12% Black or African American, 0.32% Native American, 0.15% Asian, 0.07% Pacific Islander, 1.36% from other races, and 0.48% from two or more races. 2.30% of the population were Hispanic or Latino of any race.
There were 1,430 households out of which 38.40% had children under the age of 18 living with them, 68.50% were married couples living together, 4.50% had a female householder with no husband present, and 23.60% were non-families. 22.50% of all households were made up of individuals and 11.90% had someone living alone who was 65 years of age or older. The average household size was 2.85 and the average family size was 3.35.
In the county the population was spread out with 32.00% under the age of 18, 7.70% from 18 to 24, 23.10% from 25 to 44, 21.40% from 45 to 64, and 15.90% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 103.10 males. For every 100 females age 18 and over, there were 100.40 males.
The median income for a household in the county was $34,309, and the median income for a family was $38,341. Males had a median income of $29,730 versus $19,808 for females. The per capita income for the county was $13,829. About 6.70% of families and 10.80% of the population were below the poverty line, including 13.00% of those under age 18 and 10.80% of those age 65 or over.
