[Maps of the Mullan Road]

Civil-War era maps of the eventual route of Interstate 90.

This collection of six maps (on five sheets) was published in 1861 as part of a Congressional report outlining the preliminary findings of Captain John Mullan. The Army officer oversaw the construction of what would become known as the Mullan Road, the first wagon road crossing the Rocky Mountains connecting Fort Benton (Montana) and Fort Walla Walla (Washington). The route’s construction would greatly hasten the settlement of the Pacific Northwest and encourage the establishment of the Idaho Territory in 1863. That same year, Mullan submitted a final report that contained much larger, more detailed maps.

The group consists of the following: Map of Fort Benton & Fort Walla Walla Military Road – printed in three sections across three different sheets. Field Working Sketch of the Proposed Location of Road from Camp July 14th to Coeur d’Alene Mission.” Map of Military Road from Upper Spokane [sic] Ferry to Wolf’s Lodge Prairie. and “Map of Wagon Road Connecting the Two Ferries and the Spokane [sic] River.” (final two are small maps on a single sheet).