Promontory Summit in the context of "Overland Route (Union Pacific Railroad)"

America's first transcontinental railroad (known originally as the "Pacific Railroad" and later as the "Overland Route") was a 1,911-mile (3,075 km) continuous railroad line built between 1863 and 1869 that connected the existing eastern U.S. rail network at Council Bluffs, Iowa, with the Pacific coast at the Oakland Long Wharf on San Francisco Bay. The rail line was built by three private companies over public lands provided by extensive U.S. land grants. Building was financed by both state and U.S. government subsidy bonds as well as by company-issued mortgage bonds. The Western Pacific Railroad Company built 132 miles (212 km) of track from the road's western terminus at Alameda/Oakland to Sacramento, California. The Central Pacific Railroad Company of California (CPRR) constructed 690 miles (1,110 km) east from Sacramento to Promontory Summit, Utah Territory. The Union Pacific Railroad (UPRR) built 1,085 miles (1,746 km) from the road's eastern terminus at the Missouri River settlements of Council Bluffs and Omaha, Nebraska, westward to Promontory Summit.

The railroad opened for through traffic between Sacramento and Omaha on May 10, 1869, when CPRR President Leland Stanford ceremonially tapped the gold "Last Spike" (later often referred to as the "Golden Spike") with a silver hammer at Promontory Summit. In the following six months, the last leg from Sacramento to San Francisco Bay was completed. The resulting coast-to-coast railroad connection revolutionized the settlement and economy of the American West. It brought the western states and territories into alignment with the northern Union states and made transporting passengers and goods coast-to-coast considerably quicker, safer and less expensive.

Interstate 80 (I-80) is a part of the Interstate Highway System that runs from San Francisco, California, to Teaneck, New Jersey. The portion of the highway in the US state of Utah is 197.51 miles (317.86 km) long through the northern part of the state. From west to east, I-80 crosses the state line from Nevada in Tooele County and traverses the Bonneville Salt Flats—which are a part of the larger Great Salt Lake Desert. It continues alongside the Wendover Cut-off—the corridor of the former Victory Highway—US Route 40 (US-40) and the Western Pacific Railroad Feather River Route. After passing the Oquirrh Mountains, I-80 enters the Salt Lake Valley and Salt Lake County. A short portion of the freeway is concurrent with I-15 through Downtown Salt Lake City. At the Spaghetti Bowl, I-80 turns east again into the mouth of Parleys Canyon and Summit County, travels through the mountain range, and intersects the eastern end of I-84 near Echo Reservoir before turning northeast toward the Wyoming border near Evanston. I-80 was built along the corridor of the Lincoln Highway and the Mormon Trail through the Wasatch Range. The easternmost section also follows the historical routes of the first transcontinental railroad and US-30S.

Construction of the controlled-access highway began in the 1950s, and, by the late 1970s, most of the freeway across the state of Utah had been completed. The 4.5-mile-long (7.2 km) section of I-80 between State Route 68 (SR-68, Redwood Road) and Salt Lake City International Airport was the last piece of the nearly 2,900-mile-long (4,700 km) freeway to be completed. It was opened on August 22, 1986, and was about 50 miles (80 km) from the site of another cross-country milestone in Utah, the driving of the golden spike of the first transcontinental railroad at Promontory Summit. Average daily traffic volumes in 2012 ranged between 6,765 vehicles using the freeway at SR-58 and 121,205 vehicles using the freeway at the Spaghetti Bowl in Downtown Salt Lake City. Throughout the state, the highway is also known as the Purple Heart Trail.