Why the road was bypassed in 1953
The Oatman Highway was originally designated as part of Route 66 in 1926 — the highway's federal designation followed the existing National Old Trails Road through the Black Mountains because no better route existed. Throughout the 1920s, 1930s, and 1940s the road carried the full volume of Route 66 traffic crossing between Kingman and the California state line, including the Dust Bowl migration of the 1930s and the early post-WWII tourism traffic.
By the early 1950s the road had become a significant bottleneck on the highway. The Sitgreaves Pass climb to the 3,652-foot summit and the descent down the western side included multiple hairpin turns with sight lines so short that two-truck passing was sometimes impossible, grades reaching 11% on certain pitches, and blind corners that required slow careful driving. Trucks routinely overheated on the climb (engines designed for flat-land driving could not sustain the grade), and brakes routinely overheated on the descent (the constant braking through hairpins overwhelmed contemporary brake systems).
The 1953 realignment routed Route 66 traffic to the south via Yucca and Topock — a longer route in linear miles but substantially flatter, faster, and safer for the trucking and tourism traffic of the era. The original Oatman alignment continued to exist as a county road and a tourist route but was no longer part of the federal Route 66 designation. When Route 66 itself was decommissioned in the 1980s in favor of Interstate 40, the historic significance of the surviving Oatman alignment became increasingly recognized; today the road is preserved as part of the Historic Route 66 corridor and is a major destination for Route 66 enthusiasts.