SR 142 begins in the town of Lyle, on the northern banks of the Columbia River, at a t-intersection with SR 14. The highway travels north, through a canyon carved by the Klickitat River, crossing from the eastern banks to the western banks of the river before entering the town of Klickitat. The highway continues northeast, passing through the town of Wahkiacus, before the Klickitat River turns north. The highway continues through the canyon, now paralleling the Little Klickitat River, climbing out of the canyon and passing Blockhouse Butte. The road enters the town of Goldendale, and ends at an intersection with US 97.