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. Both US 66 and US 89 split from I-40 again at Bill Williams Loop Road near McClelland Lake. The highway took the loop road for south of the Interstate before merging back into the route of I-40. At exit 161, US 66/US 89 curved northeast from I-40, then headed east on Historic Route 66 into downtown Williams. Parts of downtown Williams surrounding former US 66/US 89, including the roadway itself, are listed on the NRHP. The Williams Historic Business District and Urban Route 66, Williams, were added to the NRHP in 1984 and 1989, respectively. East of town, US 66/US 89 met the Santa Fe Railway at an underpass, then curved southeast onto an abandoned road, which tied into Mountain Man Trail in front of the Bearizona Wildlife Park. This was also the spot where US 66/US 89 intersected with the western terminus of SR 64, which headed north towards Valle and the Grand Canyon, while US 66 and US 89 continued east towards Flagstaff. Williams to Flagstaff US 66/US 89 continued east from the SR 64 junction outside Williams on Mountain Man Trail for , then crossed the present-day route of I-40 diagonally onto Deer Farm Road. Although the highway was paved in 1940, both Mountain Man Trail and Deer Farm Road have been downgraded to county maintained graded dirt roads. The highway skirted the northern shore of Davenport Lake, then crossed present-day I-40 to the south side frontage road, known as Mountain Ranch Resort Drive. US 66/US 89 crossed I-40 a second time at the spot of the current exit 171 onto a road called "Old Route 66". Unlike Mountain Man Trail and Deer Farm Road, Old Route 66 is still paved. The highway then headed east, gently winding through small pine forests, until US 66/US 89 reached the town of Parks. Small sections of Old Route