Raton Pass

Interstate 25 climbs over Raton Pass at 7,834 feet, right on the line between Colorado and New Mexico. Trinidad, Colorado sits at the north foot in Las Animas County. Raton, New Mexico sits at the south foot in Colfax County. This is the main north-south freight road between the two states. I-25 carries US 85 and US 87 over the top and links Denver and Pueblo with Albuquerque and the rest of New Mexico. There is no quick parallel route. When the pass shuts, trucks eat a long detour.

The modern crossing runs about 21.8 miles (35 km) between Raton and Trinidad with a maximum grade near 6 percent (dangerousroads.org). The climb is longer and steeper from the Trinidad side: roughly 13.9 miles gaining about 558 meters from the north, against about 11.6 miles and 332 meters from the Raton side. That sustained 6 percent works your brakes on the way down and slows a loaded rig on the way up. It gets worse fast when snow covers an ascending lane and the chain law goes active.

Weather is the recurring problem. Wikipedia describes the pass as subject to difficult driving conditions and occasional closures during heavy winter snowfalls. The triggers are blowing snow, ice, high crosswinds, and poor visibility. The elevation and exposure also build wind strong enough to close the interstate with no snow on the ground. There is no seasonal shutdown. The pass stays open year-round and closes storm by storm.

• Summit 7,834 ft (2,388 m) on I-25 directly on the Colorado/New Mexico line, between Trinidad, CO and Raton, NM (Wikipedia)
• About 21.8 mi (35 km) between Raton and Trinidad at a maximum grade near 6 percent; the Trinidad side is the longer, steeper climb (dangerousroads.org)
• I-25 carries US 85 and US 87 over the top. It is the main north-south freight route between Colorado and New Mexico, so a closure forces long detours (Wikipedia; AARoads)
• Colorado's traction and chain law zone runs from Trinidad south to the New Mexico state line. CDOT and Colorado State Patrol can require traction or chains for all vehicles there during storms (KOAA News; Colorado State Patrol)
• Closure gates sit on both sides. CDOT gates southbound I-25 from Trinidad to the line, NMDOT and New Mexico State Police gate northbound from Raton to the line, so it often shuts both ways in one storm (KOAA News; KRQE News)
• National Historic Landmark (1960), listed on the National Register of Historic Places (1966). The old corridor of the Santa Fe Trail's Mountain Branch (Wikipedia)

No fixed seasonal dates. Raton Pass stays open all year and closes only storm by storm, for heavy snow, ice, high winds, or wrecks (Wikipedia; dangerousroads.org). On the Colorado side the pass falls inside the traction and chain law zone on I-25 between Trinidad and the New Mexico state line. When a storm hits, Colorado State Patrol and CDOT activate the Passenger Vehicle Traction Law (Code 15), which requires 4WD or AWD, or mud-and-snow or winter tires with at least 3/16-inch tread. Just before a closure they can escalate to the Passenger Vehicle Chain Law (Code 16), which requires chains or an approved alternative traction device. For trucks, CDOT uses Code 17 when snow covers part of an ascending grade: single-drive-axle combinations need chains or ATDs, others need chains, ATDs, or snow tires. Code 18 requires chains on all drive axles when snow covers the full ascending lane or conditions demand it. Colorado's separate commercial Must Carry chain law runs September 1 to May 31 and covers vehicles over 16,000 pounds across roughly 1,400 centerline miles with 130 chain stations statewide, but CDOT's published Must-Carry corridor list is built around I-70 and US 40/50/160/285/550 and CO 9 and does not explicitly name I-25 or Raton Pass (CDOT, October 2025). The Code 17/18 chain law can still be activated on the pass during a storm, so carrying chains September through May is the safe practice. On the New Mexico side, NMDOT and New Mexico State Police can require chains and close the pass under state chain-law authority (NMSA 66-3-847). New Mexico has no seasonal must-carry system like Colorado's. Neither CDOT nor NMDOT publishes named formal chain-up areas for Raton Pass in the sources reviewed. Trucks chain up at pull-offs near Trinidad and near Raton and at the state-line gates. When the pass closes, CDOT typically gates southbound from Trinidad to the line while NMDOT and New Mexico State Police gate northbound from Raton to the line. Closures commonly run from about an hour to several hours. One crash closed southbound I-25 from Trinidad to the border for about 1 hour 35 minutes (KOAA News).

Raton Pass was the highest and most difficult segment of the Mountain Branch of the Santa Fe Trail, the route that crossed the Sangre de Cristo Mountains here to give 19th-century wagons access to the western territory (NPS; Wikipedia). Richens Lacy "Uncle Dick" Wootton got charters from the Colorado and New Mexico legislatures in 1865 and, starting in 1866, blasted overhangs and graded hairpin curves to build a toll road over the pass from Trinidad toward the Canadian (Red) River. Reporting cites more than 5,000 wagons using that toll road in 1866 (Colorado Encyclopedia; Legends of America).

In 1878 the Atchison, Topeka and Santa Fe Railroad beat the Denver and Rio Grande to control the pass. The railroad tunnel under it opened in September 1879, and a second tunnel followed in 1908 as traffic grew. The highway was realigned to follow Wootton's old route in 1942 and folded into Interstate 25 in the early 1960s. The rail line, now BNSF, still carries Amtrak's Southwest Chief. The pass is a National Historic Landmark (1960), listed on the National Register of Historic Places in 1966 (Colorado Encyclopedia; Wikipedia).