N.M. Stat. § 67-9-8
The state highway and transportation department shall conduct an inventory of all current New Mexico state highway designation signs on former United States route 66 and add a second designation sign reading "New Mexico Route 66", contingent upon funding pursuant to the federal Transportation Equity Act for the 21st Century, the National Scenic Byways Program and other sources. The state highway and transportation department, working with the New Mexico route 66 association and the New Mexico route 66 scenic byway coordinator in the economic development department, shall add the secondary designation "New Mexico Route 66" to all official maps of the state of New Mexico and shall complete its survey and addition of all signs prior to January 1, 2001 in celebration of the seventy-fifth anniversary of United States route 66.
NMS § 67-9-8