Box Elder County was incorporated in 1869, well before Utah became a state 27 years later. It was created in 1856 by the territorial legislature from portions of Weber County. In 1880, the borders were again re-aligned. At this time the waters and islands of the Great Salt Lake were divided between Salt Lake, Davis, Weber, Tooele and Box Elder Counties.

As with other northern Utah county areas, the first visitors to the region were fur trappers and explorers. Jim Bridger came down the Bear River from Cache Valley in 1825, becoming the first white man to greet the Great Salt Lake. The first permanent settlers, however, did not arrive until 1851 in the form of Mormon pioneers. They immediately planted crops, built homes and churches. Towns began to pop up. They utilized native materials whenever possible and quickly worked together to build up each area. In 1855, Church president, Brigham Young, named Lorenzo Snow to be the local political and ecclesiastical leader for the "Box Elder Stake of Zion."

The name "Box Elder" came from the many Box Elder trees in the area. The county seat, Brigham City, was named for Brigham Young. Other area communities, Willard, Howell and Snowville, among others, were named after local church leaders. One exception to the LDS colonization was Corinne, which was built up as a railroad and freighting town. Residents boasted of being the "Gentile Capitol of Utah."

One of the most significant events in the history of not only the area, but in the country, took place at Promontory Summit on May 10, 1869. This was where the last spike was driven to complete the country's first transcontinental Railroad, changing the form of migration for thousands of future "pioneers" and eventually changing the course of our national history. May 10 has been adopted as a commemorative day at Promontory Summit. Each year a special ceremony is held to help remember the events of that day. It has also been named a National Historic Site and welcomes many history buffs yearly. A visitor's center has been built as well as replicas of the famous locomotives, "119" and "Jupiter."