Promontory is an area of high ground in Box Elder County, Utah, 32 mi west of Brigham City and 66 mi northwest of Salt Lake City. Rising to an elevation of 4,902 feet above sea level, it lies to the north of the Promontory Mountains and the Great Salt Lake. It is notable as the location of Promontory Summit, where the First Transcontinental Railroad in the United States was officially completed on May 10, 1869.