Book cover of Inventing Idaho

Keith C. Petersen ’73 Hist.

WSU Press: 2022


“Some borders accommodate natural features, but the map of the West is essentially a vast expanse of boxlike states. And then we have Idaho. What in the world happened here?” wonders Keith C. Petersen, former Idaho state historian and associate director of the Idaho State Historical Society, in this fascinating and lively look at the decisions that formed the boundaries of the Gem State.

It took nearly 50 years for Idaho to take its eccentric shape or, as Petersen writes, acquire “the nation’s most peculiar borders.” With a fellowship from Idaho Humanities Council, he traces Idaho’s outline chronologically rather than geographically, starting with its oldest boundary. Six of the book’s eight chapters are dedicated to specific border segments, and each one of those six includes a “border story,” or case study, discussing how that particular portion has affected people’s lives.

“Understanding how Idaho got its borders is critical to understanding Idaho,” Petersen writes about what he calls the country’s “most awkwardly shaped state.” The southern border, a straight line established in 1819 dividing Idaho from Utah and Nevada, makes the most sense. It’s detailed in chapter 2.

In chapter 5, Petersen revisits some of his earlier research on Lieutenant John Mullan’s historic road, completed in 1862 with funds from the US War Department. It took some 200 soldiers and hired men more than two years to construct the route, which stretched more than 600 miles between Fort Benton, Montana, and Fort Walla Walla, and served as the first wagon road to cross the Rocky Mountains into the Inland Northwest. It’s detailed in Petersen’s John Mullan: The Tumultuous Life of a Western Road Builder (WSU Press, 2014). Today, the part of the route between Spokane and Missoula is known as Interstate 90.

Petersen explores long-forgotten stories related to Idaho’s “illogical confines” and its long struggle to connect its spindly northern panhandle to its more populated southern portion. He examines events of the past that influenced Idaho’s “bizarre boundaries” as well as how those “unwieldly borders” affected the state’s culture, politics, and economy. His well-researched exploration delves into the impacts of the French and Indian War, Mormon settlers, and more in this approachable and interesting read.


Purchase Inventing Idaho at WSU Press