Homestake Pass

Homestake Pass carries Interstate 90 across the Continental Divide about six miles southeast of Butte, Montana. It sits on the line between Jefferson County and Silver Bow County, inside the Beaverhead-Deerlodge National Forest. This is the high point of the whole 3,020-mile run of I-90 from Boston to Seattle, so when weather turns rough anywhere on that interstate, Homestake is often where it bites first.

Elevation depends on who you ask. MDT's own road weather station at the pass (station 267008, I-90 mile marker 233) lists 6,385 feet, and that is the cleanest figure to cite. Other sources put it lower or higher, from 6,329 to 6,410 feet, and a roadside Continental Divide sign reads 6,393. The point that matters for a driver is the altitude itself: snow, ice, and wind hang on here well into spring.

For truckers this is a brake-management and traction chokepoint between Butte and Bozeman. The east side drops at a 6 percent grade, with a posted 25-mph truck limit that holds for roughly four miles down the hill. Warning signs flag the grade and the S-curves before you reach them. Get your speed and your gear set at the top, because the curves and the worst crash stretch come fast on the way down.

• Highest point on all of Interstate 90, which runs about 3,020 miles from Boston to Seattle (Wikipedia; dangerousroads.org)
• MDT's road weather station 267008 at I-90 MP 233 lists the elevation as 6,385 feet (MDT RWIS station page); other sources range from 6,329 to 6,410 feet
• Eastbound descent reaches a 6 percent grade (Montana Standard / Helena IR / montanarightnow coverage)
• Posted 25-mph truck limit for vehicles 12,000 lb and over holds for about 4 miles down the grade (Montana Standard / Helena IR / montanarightnow coverage)
• Designated chain-up area on I-90 covers MM 228 to 241 in both directions (MDT Tire and Chain Laws page)
• Gravel runaway-truck ramp sits at roughly MM 238 to 239 (Flickr grade-warning caption; speed-limit coverage)
• Worst crash stretch is the S-curves between MM 236 and 238 (Montana Standard / Helena IR / montanarightnow coverage)

Montana does not run a tiered chain system. There is no R-1, R-2, or R-3 here. It is binary: MDT either calls for chains in a designated area or it does not, and the call goes out when dangerous or unsafe conditions require it. Homestake Pass is a designated chain-up area on I-90 from MM 228 to 241, both directions. When chains are required, every towing unit must put chains on the drive wheels of one axle. Between October 1 and April 30, towing units of 26,001 lb GVW or greater have to at least carry chains or approved traction devices when in areas where chains may be required (4WD vehicles are exempt, and AutoSocks count as an approved alternative). Studded tires are allowed October 1 through May 31. There is no scheduled seasonal closure of the pass. It stays open year-round, and any shutdown is unplanned and weather or crash driven, usually brief. Chain calls show up late too: on April 24, 2026, MDT required chains for towing units with the road snow-covered (NBC Montana).

The railroad came first. The Northern Pacific Railway completed its line over the area in 1889, running Logan to Garrison by way of Butte. The freeway came much later. The I-90 crossing over Homestake Pass opened in August 1966 after about two years of construction, and it was the second section of the Interstate Highway System to cross the Continental Divide.

The rail line did not last. Its steep grades and tight curvature, over 2.2 percent, made it unsuitable for modern through freight, and it went inactive in 1983. In recent years the pass has built a record of winter shutdowns and a documented state push to slow traffic down. MDT and state officials proposed dropping the car limit from 75 to 65 mph over about ten miles and reviewing the 25-mph truck limit, because the MM 236 to 238 S-curve stretch piled up the most crashes and citations (NBC Montana closure stories; Montana Standard / Helena IR / montanarightnow coverage).