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.

Outside of its Interstate concurrencies, the route is largely two lanes and rural outside of portions through major towns and cities.

Just northeast of the Langley Gulch Power Plant, US 30 begins to travel southeast at a diamond interchange, running concurrently with I-84.

[2] After leaving Boise, the freeway then serves multiple roads (including SH-21) before reaching Mountain Home.

As US 30 approaches I-84, the route turns south and east, serving Hagerman, Buhl, Filer, and Twin Falls.

[2] 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.

[6][7] 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.