Upon leaving Peach Springs, US 66 curved southeast into the Hualapai Indian Reservation. Shortly afterwards, the highway left Mohave County and continued east into Coconino County. Shortly after entering Coconino County, US 66 entered Yavapai County. The route briefly entered Coconino County again for less than , before crossing into Yavapai County for a second time, where it remained for several miles. This final crossing of the Yavapai–Coconino county line also serves as the present terminus of SR 66. From here on out, US 66 continued southeast as a county-maintained road (known as Crookton Road). This segment was previously the easternmost of SR 66, until ADOT retired this section and handed it over to Yavapai County in 1990 for maintenance.