Box Elder County is a county at the northwestern corner of Utah, United States. As of 2018, the estimated population is 54,950. Its county seat and largest city is Brigham City. The county was named for the box elder trees that abound in the county.
Box Elder County lies at the NW corner of Utah. Its west border abuts the east border of the state of Nevada and its north border abuts the south border of the state of Idaho. Its territory includes large tracts of barren desert, contrasted by high, forested mountains. The Wasatch Front lies along the south-eastern border, where the main cities are found. The terrain generally slopes to the south (toward the Great Salt Lake), although the NW corner of the county slopes to the north, allowing runoff from that area to flow to the Snake River drainage. The county’s highest point is a mountain ridge near the NW corner, at 9,180′ (2798m) ASL. The county has a total area of 6,729 square miles (17,430 km), of which 5,746 square miles (14,880 km) is land and 984 square miles (2,550 km) (15%) is water. It is the fourth-largest county in Utah by area.
In the east lie the Wellsville Mountains, a branch of the Wasatch Range. In the west is a large, mostly uninhabited desert area. The Great Salt Lake lies in the southeastern corner of the county. The combined Interstate 15/Interstate 84 runs northward in the eastern part of the county. The two routes diverge at Tremonton, with I-84 heading northwest past Snowville into cenral and western Idaho, and I-15 heading north past Plymouth and Portage into eastern Idaho.
As of the 2000 United States Census, there were 42,745 people, 13,144 households, and 10,804 families in the county. The population density was 7.44/sqmi (2.87/km²). There were 14,209 housing units at an average density of 2.47/sqmi (0.95/km²). The racial makeup of the county was 92.87% White, 0.17% Black or African American, 0.88% Native American, 0.96% Asian, 0.08% Pacific Islander, 3.45% from other races, and 1.60% from two or more races. 6.53% of the population were Hispanic or Latino of any race.
There were 13,144 households out of which 47.10% had children under the age of 18 living with them, 71.00% were married couples living together, 7.90% had a female householder with no husband present, and 17.80% were non-families. Of the 13,144 households, 281 are unmarried partner households: 247 heterosexual, 22 same-sex male, and 12 same-sex female. 16.00% of all households were made up of individuals and 7.40% had someone living alone who was 65 years of age or older. The average household size was 3.22 and the average family size was 3.63.
The county population contained 36.10% under the age of 18, 10.50% from 18 to 24, 25.40% from 25 to 44, 17.70% from 45 to 64, and 10.40% who were 65 years of age or older. The median age was 28 years. For every 100 females there were 101.70 males. For every 100 females age 18 and over, there were 98.90 males.
The median income for a household in the county was $44,630, and the median income for a family was $49,421. Males had a median income of $38,814 versus $22,435 for females. The per capita income for the county was $15,625. About 5.80% of families and 7.10% of the population were below the poverty line, including 8.30% of those under age 18 and 5.30% of those age 65 or over.
As of the 2010 census, there were 49,975 people, 16,058 households, and 12,891 families in the county. The population density was 8.70/sqmi (3.36/km²). There were 17,326 housing units at an average density of 3.02/sqmi (1.16/km²). The racial makeup of the county was 91.77% White, 0.34% Black or African American, 0.82% Native American, 0.89% Asian, 0.17% Pacific Islander, 3.77% from other races, and 2.24% from two or more races. 8.31% of the population were Hispanic or Latino of any race.
There were 16,058 households out of which 41.32% had children under the age of 18 living with them, 67.44% were married couples living together, 8.69% had a female householder with no husband present, and 19.72% were non-families. 17.16% of all households were made up of individuals and 7.39% had someone living alone who was 65 years of age or older. The average household size was 3.09 and the average family size was 3.50.
The county population contained 36.60% under the age of 20, 5.55% from 20 to 24, 25.37% from 25 to 44, 21.35% from 45 to 64, and 11.13% who were 65 years of age or older. The median age was 30.6 years. For every 100 females there were 101.59 males. For every 100 females age 18 and over, there were 96.61 males.
As of 2015, the largest self reported ancestry groups in Box Elder County were: