Interstate 15 in Idaho


Begin Samaria
End Monida Pass
Length 196 mi
Length 315 km
  • 3 Samaria
  • 13 Malad City
  • 17 Deep Creek Road
  • 22 Old Highway 191
  • 31 Downey
  • 36
  • 40 issues
  • 44 Jensen Road
  • 47 McCammon
  • 57 Income
  • 63-72: Pocatello
  • 63 5th Avenue
  • 67 5th Avenue
  • 69 Downtown Pocatello
  • 71 Pocatello Creek Road
  • 72 → Boise
  • 80 Fort Hall
  • 89
  • 93 Blackfoot
  • 98 River Road
  • 108 Shelley
  • 113 65th Street
  • 116 Idaho Falls
  • 118 Downtown Idaho Falls
  • 119 → Rexburg
  • 128 145th N
  • 135 Roberts
  • 143 Rexburg
  • 150 Hamer
  • 167 Dubois
  • 172 Sheep Station
  • 180 Spencer
  • 184 frontage road
  • 190 frontage road
  • Montana

Interstate 15 or I -15 is an Interstate Highway in the U.S. state of Idaho. The highway forms a north-south connection in the southeast of the state. The highway runs along and later through the Rocky Mountains. The highway serves two major cities in the state; Pocatello and Idaho Falls. The route in Idaho is 315 kilometers long.

  • NecessaryHome: Provides a list of all postal codes in the state of Idaho, covering area code, zip code and map for each city within Idaho.

Travel directions

De I-15 near Idaho Falls.

Just south of the hamlet of Samaria, Interstate 15 in Utah merges into the state of Idaho. The highway runs through the valley of the Malad River. The highway is quite high, at an altitude of about 1400 meters. From the highway you have a beautiful view over the surrounding mountains. At Downey, in the wide Marsh Valley, US 91 joins, which has run parallel to I-15 for some distance. At McCammon, US 30 merges into the main road to Montpelier and Kemmerer in Wyoming. The semi-desert landscape here changes into a greener area. In winter, a lot of snow can fall here, which can make driving conditions very dangerous, especially with “blowing snow”, a phenomenon that occurs after snowfall when the wind blows up the fallen snow and the visibility is very limited.

The first major city, Pocatello, has a population of 54,000 and is an important regional center in eastern Idaho. Here one crosses Interstate 86, which leads to Twin Falls and Boise to the west. After this one enters the very wide valley of the river Snake, here are quite a lot of agricultural activities. At Blackfoot the US 26 exits, which leads to Gooding. A little further on are lava formations known as “Hells Acre”. You pass the second larger city on the route, Idaho Falls, which has a population of 53,000. Here it crosses US 20, which runs west to Mountain Home, and east as a highway to Rexburg and Yellowstone National Park. People still drive through the vast Snake River Plains. Just before the border with Montana, the highway rises sharply, toMonida Pass, at 2094 meters altitude. It also crosses the Continental Divide, the watershed between the Atlantic and Pacific oceans. Although the highway is quite high here, it is not very mountainous, you are on a plateau. Interstate 15 in Montana continues here.

  • a2zDirectory: Lists popular attractions in Idaho, including parks, festivals and holidays of Idaho.


The predecessor of I-15 was largely US 91, although the section between the Utah and Downey border is mainly parallel to the former US 191.

Not all the details of the construction of I-15 through Idaho are known. Construction began in the early 1960s, with the first section opening around 1963 between Roberts and Hamer, north of Idaho Falls. Also, in about 1963, the portion of the highway over Monida Pass on the border with the state of Montana opened. Construction progressed quickly, as early as 1964 a long stretch from Pocatello to Idaho Falls had been opened, as well as a section between McCammon and Inkom south of Pocatello. By 1967, I-15 around Pocatello was in use, continuing a 175-kilometer stretch from Arimo to Hamer. Also in 1969, the first section around Malad City had been opened, as well as an extension northward from Hamer to Spencer, leaving only two short missing links on the northern section of the route, between Idaho Falls and Roberts and between Spencer and Humphrey.

The missing link north of Idaho Falls had opened by 1970, and by 1972 the missing link between Spencer and Humphrey had also opened. Also opened in 1972 a somewhat longer stretch between Malad City and Arimo, so that only the southernmost 20 kilometers from the border with Utah was missing. It is not known when this missing link was opened, probably later in the 1970s. In 1974, the network of Interstate Highways in Idaho was considered complete. Just over the border in Utah was a missing link for much longer until the late 1980s.

The highway between I-84 at Declo and I-15 at Pocatello was originally numbered I-15W. In 1980 this was renumbered as Interstate 86 in Idaho.

Interstate 15 has not been substantially modified in Idaho since the highway’s original construction. No expansions have been performed or nodes have been modified. In 2021, there was talk of widening I-15 between Pocatello and Idaho Falls.

Traffic intensities

Some 9,500 vehicles cross the Utah border every day, increasing to some 31,500 vehicles near the town of Pocatello. There are about 20,000 vehicles per day between Pocatello and Idaho Falls, quickly dropping to just 3,000 vehicles on the border with Montana in the Rocky Mountains.

Lane Configuration

Van Unpleasant Lanes Comments
Exit 0 Exit 196 2×2

Interstate 15 in Idaho