Fourth of July Pass

Fourth of July Pass carries Interstate 90 over a low summit in Kootenai County, Idaho, just east of Coeur d'Alene. It sits at about 3,070 to 3,081 feet, low by western standards, and the grade runs 5.5 percent on both the east and west sides over roughly 8 miles total. The east side is a little steeper than the west. The summit marks the western edge of the Silver Valley mining district, which runs east along the Coeur d'Alene River toward Kellogg, Wallace, and Lookout Pass at the Montana line.

For truckers, this is the first major westbound grade after you climb out of the Silver Valley, and it is a recurring winter trouble spot. Commercial traffic averages around 2,500 trucks a day, with about 10,500 cars a day, so there is far more passenger traffic here than at neighboring Lookout Pass. The numbers are modest, but the pattern is not: Idaho State Police and ITD point to Fourth of July as a place where rigs lose control on ice.

The pass does not have a fixed winter closure. There is no gate that swings shut for the season. When it closes, it closes because of a crash or weather, usually for a few hours while crews clear a blocked lane. Idaho can require chains here under state law when the road turns unsafe, and the chain-up window is typically October through April. Check Idaho 511 before you commit to the grade.

• Interstate 90 summit in Kootenai County, Idaho, east of Coeur d'Alene; western end of the Silver Valley mining district (Wikipedia)
• Summit elevation about 3,070 to 3,081 feet; sources disagree on an exact figure (Wikipedia; FoxRVTravel)
• Grade is 5.5 percent on both sides, east side slightly steeper, over roughly 8 miles total (FoxRVTravel)
• Commercial traffic averages about 2,500 trucks per day, with about 10,500 cars per day (KREM)
• Named in Idaho Code 49-948 as a pass where ITD may require chains when conditions are unsafe (Idaho Legislature)
• No fixed winter closure and no runaway truck ramp; the nearest I-90 ramp is at Lookout Pass (Idaho 511 truck-ramp list)
• ITD began a two-year I-90 resurfacing project over the pass in March 2025, running through fall 2026 (ITD news release, March 24, 2025)

The chain law on Fourth of July Pass is not on a fixed calendar. Idaho Code 49-948 names this pass and lets ITD require chains when the road is in an unsafe condition, and the statute allows the state to act at any time. In practice the chain-up season runs roughly October through April, but that window comes from ITD and secondary sources, not the statute itself, so treat it as typical rather than a hard legal date. When the chain law is active, commercial vehicles need a minimum of one tire chained on each side of one drive axle, regardless of how many drive axles the rig has, plus one axle at or near the rear of each towed unit. Cable chains and approved automatic traction devices that give equivalent traction are accepted under Idaho Code 49-104. ITD and ISP turn on roadside signs to tell truckers to chain up, and ITD lifts the requirement as soon as conditions allow to limit road damage. There is no seasonal gate closure; the pass is open year-round except during incident-driven blockages.

The road over Fourth of July Pass follows the line of the Mullan Road, built by the U.S. Army under Captain John Mullan between 1859 and 1862 to connect Fort Benton, Montana, with Fort Walla Walla, Washington Territory. On July 4, 1861, Mullan's crew celebrated the Fourth of July atop this summit while building the road. That is how the pass got its name.

The Mullan Road was added to the National Register of Historic Places in 1975, and the American Society of Civil Engineers designated it a historic civil engineering landmark in 1977. The corridor is still being worked on. In March 2025 ITD began a two-year resurfacing project covering the roughly 8-mile stretch of I-90 from Wolf Lodge over Fourth of July Pass, with summit illumination, drainage upgrades, and concrete-barrier replacement, running through fall 2026.