At 17.3 miles (27.8 km) long, it connects the towns of Newton, Clarkston, Trenton, and Richmond to US-91 and SR-23 in northern Cache County.

The route starts at its intersection with SR-23 in Newton and travels about 5 miles (8.0 km) northwest to Clarkston.

Here the route turns east and travels just over 12 miles (19 km) through Trenton and ends in Richmond at the intersection with US-91.

[3] In 1969, SR-170, which ran from Clarkston via Trenton to Richmond was absorbed into SR-142, and SR-170 was deleted.

This completed the current route of SR-142 as it runs today.