List of Idaho State Highways

Highway markers for State Highways 3, 75 and 200
Highway names
Interstates:	Interstate X (I-X)
US Highways:	U.S. Route X (US-X)
State:	Idaho State Highway X (SH-X)
System links
State Highways in Idaho Interstate U.S. State

The Idaho Transportation Department is responsible for the establishment and classification of a state highway network, including 5,000 miles (8,000 km) of roads that are classified as Interstate highways, U.S. highways, and state highways.

Instead of numbering its highways, Idaho had a system of lettered Sampson Trails in the 1920s. They were marked by Charles B. Sampson of Boise at no expense to the state. By the mid-1930s, the state had adopted a more standard system of numbered state highways.

The following trails were marked: