This ecoregion is a portion of the very dry mountain habitat in the western United States, but is considerably lower and more gently sloping than the surrounding ecoregions.

Mostly because of the available water for irrigation, a large percent of the alluvial valleys bordering the Snake River are in agriculture, with sugar beets, potatoes, alfalfa, and vegetables being the principal crops. Cattle feedlots and dairy operations are also common in this river basin.

Except for the scattered barren lava fields, most of the plains and low hills in the ecoregion have a sagebrush-grassland vegetation, now used primarily for cattle grazing.

The Lewis and Clark Expedition crossed westwards into the Snake River waterway in 1805 and they gave the river the name of Lewis River or Lewis Fork because Meriwether Lewis was the first of the group to sight the river. They also make note of a tribe of Shoshone natives living along the river who were known as the Snake Indians and learned that these indigenous people called the river the Yam-pah-pa after the herb growing along its banks.

Later, Wilson Hunt of the Astor Expedition named the waterway the name Mad River, others called it the Shoshone River or Saptin River. However, the name Snake River was given to this waterway by explorers because the Shoshone tribe made a S-shaped gesture with their hands representing swimming salmon. The explorers misunderstood that gesture to represent a snake and gave the river the name that it has today.

Lava Flow Campground

Hagerman Fossil Beds National Monument