East of Parma, US-20/26 runs along the north bank of the Boise River for more than a dozen miles before crossing I-84 at the city of Caldwell—home of the mid-August Caldwell Night Rodeo (208/459-2060). A century ago, Caldwell was the site of the 1905 bomb-blast murder of former Idaho governor Frank Steunenberg. Blamed on left-wing Wobbly union activists, including “Big Bill” Haywood, who’d been organizing Idaho’s miners and loggers, the murder was the story behind J. Anthony Lukas’s sprawling book Big Trouble: A Murder in a Small Western Town Sets Off a Struggle for the Soul of America.

From Caldwell, you can follow the freeway into Boise, but it’s more interesting, and depending on traffic possibly even quicker as well, to stay on US-20/26 (a.k.a. Chinden Boulevard), which runs right atop the old Oregon Trail into downtown, past corn and wheat fields that have been rapidly sprouting golf course estates, a Hewlett-Packard factory, car-parts stores, and the usual Asphalt Nation sprawl.