U.S. Highway 30 (US 30) runs northwest–southeast across the southern half of lower Idaho for 455.481 miles (733.026 km). US 30 enters the state from Oregon across the Snake River in Fruitland and exits into Wyoming east of Dingle. US 30 runs through the large population centers of Boise, Twin Falls, and Pocatello, as well as a plethora of smaller communities from Fruitland to Montpelier. The Thousand Springs Scenic Byway is a picturesque section of US 30 in southern Idaho between the towns of Bliss and Buhl, dipping down into the Hagerman Valley and a canyon of the Snake River.
The highway has four extensive concurrencies with Interstate Highways: Interstate 84 (I-84) twice, I-86, and I-15. Outside of its Interstate concurrencies, the route is largely two lanes and rural outside of portions through major towns and cities.
Route description
Oregon state line to Boise
After crossing the Snake River, US 30 enters Fruitland as Northwest 16th Street before intersecting US 95. The route then turns south along US 95 (Whitley Drive in Fruitland). Just north of the I-84 interchange, US 30 turns east toward New Plymouth. In New Plymouth, US 30 bends south, then southeast, and then south again. Just northeast of the Langley Gulch Power Plant, US 30 begins to travel southeast at a diamond interchange, running concurrently with I-84. Along the way, they serve Sand Hollow with one diamond interchange. Just north of Caldwell, US 20 and US 26 enter the freeway southeastward, joining with the concurrency. Entering Caldwell, they then serve I-84 Business/State Highway 19 (I-84 Bus./SH-19) and 10th Avenue before both US 20 and US 26 leave the freeway together on Franklin Road. In Nampa, I-84 and US 30 then serve SH-55, which then travels eastward concurrently with the two routes. The three routes then serve Northside Boulevard, Franklin Boulevard, and Garrity Boulevard (I-84 Bus.). In Meridian, the freeway concurrency serves SH-69. At the next exit, SH-55 leaves the concurrency. Then, in Boise, the freeway comes across I-184 which serves Downtown Boise. Between exits 52 and 54, the freeway is situated north adjacent to Boise Airport, with exit 53 serving the main terminal. Also, at exit 54, US 20 and US 26 rejoin the freeway.[2]
Boise to Downtown Pocatello
After leaving Boise, the freeway then serves multiple roads (including SH-21) before reaching Mountain Home. In Mountain Home, the freeway serves I-84 Bus. At the next exit, US 20 leaves the freeway alone. The three remaining routes go on to serve several more roads (such as I-84 Bus. and SH-78). Then, in Bliss, US 30 leaves the freeway and enters the Thousand Springs Scenic Byway. As US 30 approaches I-84, the route turns south and east, serving Hagerman, Buhl, Filer, and Twin Falls. North of Kimberly, the route then leaves the byway. In Burley, the route then intersects SH-27 and SH-81. In Heyburn, the route rejoins I-84 while also intersecting SH-24. They then serve SH-25/SH-77 at the same interchange. Then, US 30 transitions from I-84 to I-86 on a modified interchange. Both I-86 and US 30 serve more roads and places (including Register Rock, I-86 Bus., SH-39, and Pocatello Regional Airport). At exit 58, US 30 leaves the freeway as it approaches Pocatello. At this point, US 30 travels along a road parallel to the railroad. Along the way near downtown, it then begins to run concurrently with I-15 Bus. and US 91. Shortly after that, the concurrently splits into a one-way pair.[2]
Thousand Springs Scenic Byway
The Thousand Springs Scenic Byway is a picturesque section of US 30 in southern Idaho between the towns of Bliss and Buhl, dipping down into the Hagerman Valley and a canyon of the Snake River. The byway takes its name from the numerous streams and rivulets springing forth out of the east wall of that canyon, many of them plainly visible from the road, with the panoramic river in the foreground. These springs are outlets from the Snake River Aquifer, which flows through thousands of square miles of porous volcanic rock and is one of the largest groundwater systems in the world.[3][4] The aquifer is believed to be fed by the Big Lost River which disappears into lava flows near Arco, about 90 miles (140 km) northeast of Hagerman.
Downtown Pocatello to Wyoming state line
The concurrency returns to a two-way street. It then comes across I-15 at a diamond interchange. At this point, both U.S. Highways continue southeast along I-15 while I-15 Bus. ends there. The three routes (I-15, US 30, and US 91) then serve even more places such as another I-15 Bus. in Inkom. At exit 47, US 30 leaves the freeway to serve McCammon. At this point, US 30 begins to meander across several mountains. Between Alexander and Soda Springs, SH-34 runs concurrently with US 30. US 30 then serves more towns through the rest of the state, especially Montpelier. In Montpelier, US 89 briefly runs concurrently with US 30.[2]
Construction of I-80N (now I-84), a freeway that would parallel US 30 between Portland, Oregon, and northern Utah, began in the 1960s under the Federal-Aid Highway Act of 1956.[6] Various sections of US 30 were relocated onto the new freeway as sections opened over the following two decades. The two suffixed routes were eliminated in 1972 in favor of US 30 remaining on the northern route while generally following I-80N and I-15W (now I-86).[8] A section through Meridian and Downtown Boise was removed in 1980, replaced by a longer overlap with I-84.[9][10] Five years later, the section from Caldwell to Nampa was replaced with I-84 Bus.[11]
^Special Committee on U.S. Route Numbering (June 26, 1985). "Route Numbering Committee Agenda" (Report). Washington, DC: American Association of State Highway and Transportation Officials. p. 514. Retrieved February 11, 2023 – via Wikisource.
^"State Highway System Route: 0095"(PDF). Idaho Transportation Department Milepoint Log. Idaho Transportation Department. January 12, 2016. Archived(PDF) from the original on August 31, 2021. Retrieved November 7, 2020.
^"State Highway System Route: 0084"(PDF). Idaho Transportation Department Milepoint Log. Idaho Transportation Department. January 12, 2016. Archived(PDF) from the original on February 27, 2021. Retrieved November 7, 2020.
^"State Highway System Route: 0015"(PDF). Idaho Transportation Department Milepoint Log. Idaho Transportation Department. January 25, 2016. Retrieved November 7, 2020.
