The route climbs north at a gentle grade until it turns east, where it begins to offer panoramic views of San Bernardino.

After meeting State Route 138 at Mount Andreson Junction south of Crestline, the expressway reverts to a two-lane mountain road.

At that point, Route 18 again runs along a lengthy mountain ridge, offering more spectacular scenery at an even higher elevation.

At its west junction with State Route 38 near the west corner of Big Bear Lake, Route 18 jogs across a dam and travels along the south shore of Big Bear Lake.

In 1944, prior to the construction of I-10, the southern terminus of SR 18 began at the intersection of E Street and Colton Avenue.

In 1984, the portion of SR 18 running concurrently with Interstate 15 in Victorville was removed from the legislative definition.

[2] Before 1964, SR 18 continued south of San Bernardino to Lakewood, via La Cadena Drive, Magnolia Avenue, 6th Street, Pomona-Rincon Road, Santa Ana Canyon Road, Lincoln Avenue, Carson Street and Lakewood Boulevard.

[2] 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.