Colorado State Highway 66

State Highway 66
Map of northern Colorado with SH 66 highlighted in red
Route information
Maintained by CDOT
Length	22.7 mi[1] (36.5 km)
Major junctions
West end	US 36 / SH 7 southeast of Lyons
Major intersections	US 287 in Longmont I-25 / US 87 near Longmont
East end	US 85 in Platteville
Location
Country	United States
State	Colorado
Counties	Boulder, Weld
Highway system
Colorado State Highway System Interstate US State Scenic
← SH 65 → SH 67

State Highway 66 (SH 66) is a 22.7 mi (36.5 km) long east-west state highway in Boulder and Weld counties in Colorado. The highway extends from the foothills of the Rocky Mountains at a junction with U.S. Route 36 (US 36) and SH 7 southeast of Lyons, proceeding east through the northern edge of Longmont, to Platteville where it ends at US 85. Although a number of western states retain their "state highway 66" as the decommissioned US 66, the "Mother Road" did not run through Colorado, and SH 66 has no connection to the famed Historic Route 66.