Colorado State Highway 257

The route begins at SH 60 in the western part of Milliken, a town in central Weld County. It then heads northward, crosses the Big Thompson River, a tributary of the South Platte River then enters Greeley.

At Greeley, SH 257 has two interchanges with US 34[2] and U.S. Route 34 Business (US 34 Bus.). Because the intersection is so close to the terminus of US 34 Bus., the two interchanges are just 0.3 miles apart.[3] Both are diamond interchanges, but at US 34 there are only entrance ramps from the east side.[3]

The snow-capped peaks of the Front Range. Also visible is a bike path near SH 257 in Windsor.

It then heads northward, and begins to curve northwest[4] over the Cache la Poudre River and into Windsor. It intersects SH 392 and abruptly turns west, beginning a concurrency at Main Street; about a mile later SH 257 abruptly turns back northward at 7th Street, ending the concurrency. It then heads all the way north to SH 14, where it terminates. No towns exist on the route from Windsor to SH 14.

The route was established in 1939 with several differences. The route went north to Windsor from Milliken, then turning west to SH 185. SH 185 was then deleted and replaced with Interstate 25, and SH 257 was readjusted so that it went north to SH 14. The route was paved by 1954. A spur south of Johnstown was eliminated a year later. The interchanges at US 34 and BR 34 were built in 1998.[5]

In November 2009, a new traffic signal was installed at the intersection with Garden Drive in Windsor. The construction cost about $350,000.[6]

Because of congestion around the US 34 and BR 34 interchanges, a bus rapid transit system has been planned to be built in Greeley.[3]

The entire route is in Weld County.

Location	mi	km	Destinations	Notes
Milliken	0.000	0.000	SH 60	Southern terminus
Greeley	5.124	8.246	US 34
	5.423	8.727	US 34 Bus.
Windsor	10.595	17.051	SH 392 east	Southern end of SH 392 concurrency
	11.580	18.636	SH 392 west	Northern end of SH 392 concurrency
​	18.487	29.752	SH 14	Northern terminus
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus