From Grand Coulee, the roadway travels southeast to end at SR 21 northwest of Wilbur.

From Leahy, the highway travels northeastward through grasslands with few farms before turning southeast to intersect its Crown Point spur near the Grand Coulee Dam.

SR 174 continues to the Grand Coulee Dam federal reservation and state maintenance ends through the area.

[5] SR 174 had previously been parts of various county roads until 1937, when Washington established a system of primary and secondary highways throughout the state.

[10] A branch of SSH 10B from its main route to the Crown Point viewing area of the Grand Coulee Dam was added in 1955.

[1][15] The older spur route is located near the Grand Coulee Dam and connects SR 174 to Crown Point State Park, part of the Lake Roosevelt National Recreation Area, within the community of Coulee Dam.