Interstate 86 (I-86) is an east–west intrastate Interstate Highway located entirely within the state of Idaho. It runs approximately from an intersection with I-84 east of Declo in rural Cassia County, to an intersection with I-15 in Chubbuck, just north of Pocatello. The highway is part of the main route from Boise and Twin Falls to Idaho Falls and the upper Snake River region. I-86 runs through a sparsely populated region along the south side of the Snake River and is mostly concurrent with US Highway 30 (US-30), which it replaced in the 1970s. It passes through American Falls at its midpoint and has a business route that serves the city center. The highway also serves Minidoka National Wildlife Refuge, Massacre Rocks State Park, the Fort Hall Indian Reservation, and Pocatello Regional Airport. The highway follows a section of the historic Oregon Trail, which was paved and incorporated into US-30N in 1926. Under the original numbering proposal for the Interstate Highway System released in 1957, the highway was supposed to be part of Interstate 82N (I-82N), but it was instead designated as Interstate 15W (I-15W). The first section of the freeway, near American Falls, was completed in 1959. Other sections near Chubbuck and Pocatello were opened in 1968. I-15W was renumbered to I-86 in 1978, shortly before construction of its final section between Raft River and American Falls commenced. The highway was dedicated and opened to traffic on October 11, 1985. Route description I-86 begins at an interchange with I-84 and US-30 northeast of Declo. From the interchange, I-84 continues west toward Twin Falls and Boise and southeast toward Salt Lake City, Utah. I-86 travels east, concurrent with US 30, through rural Cassia County for about to its first exit at Raft River near a crossing of the river of the same name. From Raft River, I-86 follows the Snake River upstream through Minidoka National Wildlife Refuge and crosses into Power County. The freeway continues northeast between the Snake River and the Sublett Range and passes a set of rest areas near Massacre Rocks State Park, one of the state's most popular tourist attractions. Near Neeley, I-86 passes a wind farm and intersects State Highway 37 (SH-37), which provides a southerly connection to Rockland. A business route of I-86 also terminates at the interchange and continues along the north side of the freeway as it approaches the city of American