The route briefly enters Maricopa County, where it junctions with State Route 88, which takes over the Apache Trail designation to Apache Junction.

SR 188 then re-enters Gila County, continuing through Tonto Basin and Punkin Center.

A two-lane steel arch bridge upstream from the dam has now replaced this routing.

State Route 188 has been widened to a multi-lane highway along part of its length.

On August 20, 1999, it extended over part of SR 88, completing its current length.