Snoqualmie Pass

Interstate 90 crosses the Cascades at Snoqualmie Pass, about 50 miles east of Seattle, topping out at 3,022 feet just north of Exit 53. Of Washington's three year-round crossings of the Cascades, Snoqualmie is the lowest and by far the busiest, and it is the only interstate over the range. Almost everything moving between Puget Sound and eastern Washington runs through here.

Freight drives the traffic. WSDOT counts roughly 35 million tons of cargo worth about $500 billion over the pass each year, and trucks haul close to 59 percent of that tonnage. Average daily traffic runs around 29,000 to 34,000 vehicles. The climb is long and steady rather than steep, and WSDOT has added truck-climbing lanes, including one westbound near the Kachess River, to keep slow rigs out of the faster traffic. One thing to plan for: west of the summit the descent runs partly on bridge structure with no runaway-truck ramp on that stretch, so manage your brakes and gearing on the way down.

The pass stays open year-round, but winter is a fight. About half a dozen avalanche chutes cross the corridor, most of them on the west side, and WSDOT closes the road to run avalanche control. Add heavy snow, spinouts, and the occasional jackknifed truck and you get the closures the pass is known for.

• Summit 3,022 ft on I-90, the lowest and busiest of Washington's three year-round Cascade crossings
• Roughly 35 million tons of freight worth about $500 billion crosses each year; trucks haul about 59 percent of it (WSDOT)
• Average 29,000 to 34,000 vehicles a day
• Trucks over 10,000 lb must carry chains Nov 1 to Apr 1 between North Bend (MP 32) and Ellensburg (MP 101), plus two spares (WSDOT)
• About half a dozen avalanche chutes cross the corridor; WSDOT closes the road for avalanche control

WSDOT sets the rules and the Washington State Patrol enforces them. Any vehicle over 10,000 pounds has to carry chains from November 1 to April 1 on I-90 between North Bend at milepost 32 and Ellensburg at milepost 101, no matter the weather, plus at least two spare chains. WSDOT posts four levels as conditions worsen. Traction tires advised comes first, then traction tires required, which is the point where heavy vehicles over 10,000 pounds have to chain up. Above that is chains required for most vehicles, and finally chains required on all vehicles, including 4WD and AWD, which is the level right before WSDOT closes the pass. Chains have to be two-sided metal, not plastic. Eastbound chain-up areas sit around mileposts 34 and 47 east of North Bend. Skipping a required chain-up can cost up to $500, and one un-chained truck that spins out can close the whole pass.

The first road over the pass, the Sunset Highway, opened on July 1, 1915 as Washington's first auto route across the Cascades, following an older wagon road and a Native American trail that I-90 still roughly traces. Crews began plowing and keeping the road open through winter in 1931.

The piece of history truckers drove past for decades was the Lake Keechelus snowshed, built in 1950 to shield the highway from avalanches. WSDOT removed it in 2014 and replaced it with two avalanche bridges about 365 meters long, engineered so sliding snow and falling rock pass underneath, between the supports. For roughly 40 years WSDOT brought the slopes down with military artillery, including a 105mm recoilless rifle and an M60 tank. In 2025 it started swapping the guns for solar-powered remote avalanche towers that are safer and cut the closures shorter.