At the spot where the I-40 Business Loop turns south to become SR 89, there used to be an intersection where US 66 met at a junction with US 89. US 89 shared a wrong-way concurrency with US 66 between Ash Fork and Flagstaff. Both US 66 and northbound US 89 continued straight east from this intersection on to a highway alignment which no longer exists. The former highway straddled the north side of I-40, at times, often joining and leaving the present westbound lanes of the Interstate. East of Ash Fork, the route left the high desert terrain and entered a mountainous area, covered with Ponderosa pine forests. US 66/US 89 left I-40 around exit 149, heading northeast along an abandoned section of highway through the Monte Carlo truck stop. Approximately from the Interstate, the highway turned straight east for , then wound southeast for , crossing over the Interstate. The old highway made a broad curve less than southeast of I-40, then curved northeast, merging back into the route of I-40. Today, part of this section of former US 66/US 89 is listed on the National Register of Historic Places (NRHP) as Abandoned Route 66, Ash Fork Hill.