[2] The route progresses northward, passing through a large commercial district in Tecate, California.

The highway heads to an intersection with Thing Road, where it turns to the northeast and out of the commercial district.

The route continues to the northeast, intersecting with Humphries Road, where the surroundings become highly undeveloped.

[7] In the 1964 state highway renumbering, SR 188 was officially defined as "the south end of Fallen Leaf Lake to Route 89 near Camp Richardson";[8] this was later removed in 1965.

[15] The Tecate border crossing expanded through the opening of the Tecate Commercial Vehicle Enforcement Facility, including truck scales; this was completed in 2008, with past expansions to the crossing having been completed in 2004 and 2005.