Legend
| 1926-1929 | Alignments used as the 1926 alignment or constructed between 1926 and 1930. |
|---|---|
| 1930-1939 | Alignments constructed in the 1930's. |
| 1940-1984 | Alignments constructed in the 1940's and later non-interstate alignments. |
| Interstates | Interstate alignments (Typically not covered in the descriptions) |
| POT | One of the predecessors of Route 66: Pontiac Trail in Illinois. Only shown if not under the 1926 alignment. |
| OZT | One of the predecessors of Route 66: Ozark Trail in Missouri and Oklahoma. Only shown if not under the 1926 alignment. |
| SFT | One of the predecessors of Route 66: Santa Fe/Pecos rail in New Mexico. Only shown if not under the 1926 alignment. |
| CAM | One of the predecessors of Route 66: Camino Real in New Mexico. Only shown if not under the 1926 alignment. |
| NOT | One of the predecessors of Route 66: National Old Trails in New Mexico, Arizona and California. Only shown if not under the 1926 alignment. |
| solid line | Drivable public road. Use common sense before entering, conditions can change. |
| dashed line | Drivable, with caution and appropriate vehicle, might require a high clearance and/or a real 4x4 off-road vehicle. CAUTION advised. |
| dotted line | Undrivable due to the alignment destroyed, becoming private property or just unreachable. NOT ADVISED to attempt to drive. |
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