Mullan Road

Mullan Road is an Idaho historical marker in Kootenai County, dedicated 2025.

I-90 (E Alder Creek Rd, Near Exit 28), milepost 28

Get directions ↗Start a road trip Historical trails

Walk the Mullan Road, one of the Northwest's most significant routes. Take the side road to your left. From 1858-62, John Mullan's Army road crew built the Northwest's first engineered highway, connecting Fort Benton with Fort Walla Walla, 625 miles long. Idaho’s portion of Interstate 90—the “Captain John Mullan Highway”—roughly follows that road. Mullan's crew spent Independence Day 1861 here, giving Fourth of July Summit its name. They carved that date into a white pine. The famed Mullan Tree became a popular tourist stop before foresters removed the diseased tree in 1988.

TodayHistorical map

Slide toward Today to fade the historical sheet and see the modern map underneath.

David Rumsey Map Collection, Stanford Libraries

Historical maps covering this location

1856 · Washington And Oregon. (David Rumsey Map Collection, Stanford Libraries)
1857 · Washington and Oregon (and Idaho and Montana) (David Rumsey Map Collection, Stanford Libraries)
1859 · Department of Oregon. Map of the state of Oregon and Washington Territory (David Rumsey Map Collection, Stanford Libraries)
1861 · Rocky Mountains to Puget Sound. (David Rumsey Map Collection, Stanford Libraries)
1927 · Spokane, Seattle. (David Rumsey Map Collection, Stanford Libraries)

Department of Oregon. Map of the state of Oregon and Washington Territory, 1859, covering the location of Mullan Road, with a pin at the marker's coordinates — Department of Oregon. Map of the state of Oregon and Washington Territory, 1859, covering this location. David Rumsey Map Collection, Stanford Libraries. The pin is ours, placed from the marker's coordinates.

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The Idaho Highway Historic Marker program is administered by the Idaho Transportation Department (ITD) in partnership with the Idaho State Historical Society (ISHS). Marker texts and locations are reproduced with the written permission of both offices.
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