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| US 660 twice renumbered | |||||
| Previous US 560's: |
US 560 #1: Appears in the 1925 plan, running from US 60 (now NM 118) Gallup NM to US 450 (now State St) just east of Cortez CO.
In 1926, AASHO approved a 6th branch off of US 60. Because this was east of the 5th branch, AASHO made this new branch US 560 and renumbered the 1925 US 560 as US 660. Today it is the US 491 corridor. The 1926 New Mexico documents from the AASHO database have a single reference to 660, but in a way that made it seem like it could have been a typo, since they also didn't mention 560 moving to the new branch. However, the March 2003 New Mexico application to renumber US 666 had a summation of the entire history of that corridor and had this passage:
 2003 application to AASHTO There is a preliminary AASHO map that shows the corridor as US 560 with 666 handwritten on it, as well as the 1926 Colorado official map showing it as US 560.
US 560 #2: Appeared in July 1926, running from US 370 (now NM 1) San Antonio NM to US 360 (now US 70) Hondo NM. When the US 60-66 swap occurred in late 1926, US 560 was renumbered as US 566. Today it is part of the US 380 corridor.
 1926 National Highways Association
 1927 RMcN | ||||
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Page last modified 10 February 2026