Interstate 15 – Idaho

The Interstate 15 journey

Originally known as Route 3, Interstate 15 begins at the Utah State Line north of Logan, Utah, continues north through Pocatello and Idaho Falls to the Idaho/Montana state line.

On a regional scale, this stretch of 196 miles later became Interstate 15.

Nationally, I-15 is the fourth longest north-south transcontinental highway, traveling through Montana, Idaho, Utah, Arizona, Nevada and California. The highway is a non-stop link between San Diego and the shipping ports there through the western slope of the northern Rockies.

This scenic highway begins in Idaho's southeastern highlands, on the northern tip of Utah’s Wasatch Front. It shoots like an arrow directly north, with the first major Idaho stop in Malad (pronounced mah-LAD), just before Malad Summit. The highway continues north through the Caribou National Forest, splitting islands of timber stands interspersed with high wheat fields and bitter brush ranges.

Over the summit, the highway follows the Marsh Creek and then Portnuef (PORT-nuff) River before taking a 90-degree jog west at Inkom. The interstate closely follows the Portneuf River to Pocatello, where it veers north and east of the city, joining with Interstate 86 at the suburb of Chubbuck.

The highway continues north through the Fort Hall (Shoshone-Bannock) Indian Reservation, which offers travelers numerous shopping and entertainment amenities, including an Indian gambling casino, popular with eastern Idaho and Utah residents.

Continuing north, vacationers typically leave I-15 at Idaho Falls to join State Highway 20, which leads northeast to Yellowstone National Park. Meanwhile, the Interstate rises gradually toward Montana as open fields give way to stands of lodge pole pines.

Winter is an extended season in this region, with snow flurries sometimes beginning in early September and snow remaining on the ground well into May at some higher elevations.