The county was named for the box elder trees with which the county abounds. Box Elder County borders the state of Idaho to the north, Cache County and Weber County to the east, Davis County to the southeast, Tooele County to the south, and the state of Nevada to the west.
Box Elder County lies on the north end of the Great Salt Lake, covering a large area north to the Idaho border and west to the Nevada border. Included in this area are 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.