Interstate 84– Idaho

Interstate 84 was commissioned on May 1, 1980, to replace Interstate I- 80N as part of a nationwide effort to eliminate split and sufrixed routes. I-84 generally follows U.S. 30 from Portland, Oregon, east to Rupert, Idaho. East of Rupert, U.S. 30 initially split into two routes – U.S. 30N and U.S. 30S. I-84 replaces U.S. 30S from Rupert southeast to Echo Junction, via Ogden, Utah.

I-84 violated the Interstate Highway Numbering Convention by being south of I-82. The Portland, Oregon, segment of then I-80N was proposed to run on the Mt. Hood Freeway. Plans for that route were officially dropped in 1978 after a successful freeway revolt.

The Interstate 84 journey

Idaho Route 2, (now Interstate 84 through southern Idaho) begins at the Idaho/Oregon state line near Ontario and continues across the state to Pocatello. The longest continuous section of interstate in Idaho, this highway was later changed to “80 North (80N)” and subsequently Interstate 84. However, the section of highway that continues from east of Burley to Pocatello was later renamed Interstate 86; I-84 continues its southeasterly course from the intersection at Burley into Utah.

Interstate 84 from the Oregon/Idaho state line to Snowville, Utah, encompasses 276 miles of divided four-lane highway, the longest continuous span of interstate roadway in Idaho. It drives southward as it begins its “smile” route across the southern half of the state. Some call the complete drive from the Boise Valley to Idaho Falls “’round the horn” of Idaho.

The distance between Boise and Idaho Falls by air is only 210 miles, but the Sawtooth Mountains with granite peaks of more than 10,000 feet above sea level, make a direct motor route impossible. Interstate 84/86 follows the ancient corridor carved by the Snake River, swinging about 60 miles to the south, touching the outskirts of Twin Falls as it rolls over canyon country and long, black lava flows.

In the western end of Interstate 84, Treasure Valley residents use the interstate for everyday commuting as they jockey through rush-hour traffic every weekday. The outer limit for most commuters working in Boise is Fruitland, about 60 miles to the west/northwest; although most commuters come from the Canyon County towns of Caldwell and Nampa, and the expanding western Ada County city of Meridian.

A short spur of Interstate 84, I-184, allows freeway access to the immediate downtown area. Unfortunately for commuters -- but fortunately for Boise-area sunglasses distributors -- the usual commute puts the sun directly in driver’s eyes, both driving in to Boise in the morning and home again in the evening.

Continuing east on Interstate 84, the road grade rises up to a high plateau, where it stays for the next 50 miles. Just 20 years ago, this was open gopher country, but it is increasingly being populated by industrial users and, even more recently, planned residential development. The highway is the main military route to Mountain Home and Mountain Home Air Force Base, a major military installation since World War II with an emphasis on tactical fighter aircraft.

Southeast of Mountain Home, the interstate leaves the plateau and rejoins the Snake River’s steady and wide upstream cascade. The river falls away to the south after the town of Bliss where the Interstate instead takes a more direct route on the flats along the north side of the river.

The interstate bypasses the city of Twin Falls, running a few miles to the north. But the geographical barrier has always been the Snake River Canyon, a 500-foot chasm between the interstate and the city.

In 1960, as the interstate route was being planned and selected, city leaders said the route would deal an “economic blow” to the region. Representing the Twin Falls Chamber of Commerce, John E. Hahn said Highway 30 had served the city well since the beginning of the paved roadway system and that the new route “called for a hard selling job by the citizens to lure the tourist into the area.”

Twin Falls had been served by a bridge from as early as 1927, but in 1974, the 1,500-foot long Perrine Bridge was constructed as a modern replacement. Just east of this spot is where Evel Knievel attempted his failed jump across the Snake River in that same year.

I- 84 continues eastward through a network of small farming towns; Hansen, Hazelton, Burly, Paul, Heyburn and Rupert. The route skirts south of the Craters of the Moon National Monument, a black anti-oasis of bare lava that quickly shreds almost anything that tries to cross its path. A few miles past the Declo interchange is the junction of Interstate 84, which dives down into Utah toward Salt Lake City, and Interstate 86, which begins a gently swooping curve to the north in an ascension that will ultimately lead toward Montana.

Interstate 86 from the I-84 interchange to Pocatello is where eastern Idaho unofficially begins. The Snake River, crossed east of Burley, reemerges on the northern side of the highway. There are few stops and fewer people along this stretch of road, which climbs slowly with the braiding river. The Coldwater area south of American Falls appears to be one of the more desolate corners of the state as the road bends gently north toward Pocatello. Wildlife is abundant, with deer, whistling swans and other types of riparian habitat for birds and mammals.

Massacre Rocks State Park, with its dark jutting cliffs towering above the river, attracts climbers from around the globe. South of American Falls, a state rest stop and interpretive center showcases the visible Oregon Trail ruts. I-86 between Raft River and American Falls was the final section of I-84 to be completed when it was finished in the 1980s. The final section was finally laid down between Register Rock and Eagle Rock.

The American Falls Reservoir itself become visible as a huge body of water in the high desert, feeding the irrigation needs of millions of acres of potato and beet farmers along the valley. The gateway to Pocatello comes into view as an industrial center -- FMC and Simplot phosphate processing plants -- rises on the eastern horizon.

Pocatello itself is growing beyond the boarders of the Interstate, which once hemmed the community’s western edge. Although not yet a commuter artery, as it is in Boise, the Flying Y connection between east-west I-86 and north-south I-15 is nevertheless a busy regional crossroad.