Running from State Route 90, Imperial Highway, in Brea to State Route 71 in Chino Hills, SR 142 is a popular shortcut from the business centers of Brea and surrounding Orange County to the Inland Empire.

The road has multiple tight curves, so travel is not recommended for long vehicles, such as big rigs.

SR 142 continues into the community of Olinda before crossing into the Sleepy Hollow area of the city of Chino Hills in San Bernardino County.

[8] In 1933, a road from Brea to Chino was added to the state highway system.

Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage.