The Journals of the Lewis and Clark Expedition (edited by Gary Moulton) — The Corps of Discovery passed through this stretch of the Missouri twice, once heading west in 1804 and again eastbound in 1806. The journals record both passages in careful detail: the confluence of the Yellowstone, the behaviour of the river, the peoples they met. Reading the original accounts alongside a visit to Fort Union and Fort Buford gives the landscape an entirely different depth.
Colter: The True Story of the Best Exploration in American History by Larry Len Peterson — John Colter left the Lewis and Clark expedition near the mouth of the Yellowstone and went on to become the first non-indigenous person to see what is now Yellowstone. Peterson's account traces the fur-trade era in which Fort Union was built, and the world of the mountain men who made the upper Missouri one of the most contested and storied stretches of wilderness in North America.
The Heartbeat of Wounded Knee: Native America from 1890 to the Present by David Treuer — Fort Buford, where Sitting Bull surrendered in 1881, is one small node in a vast and painful history. Treuer's book, written by an Ojibwe author, is the best single-volume rebuttal of the myth that Native American history ends with the nineteenth century. It belongs in your bag before you visit any of the sites in this region.
Oil on the Brain: Adventures from the Pump to the Pipeline by Lisa Margonelli — The Bakken boom reshaped Williston completely and left marks that are still visible in the built environment. Margonelli's investigation into how oil moves through the world is a clear-eyed companion to the experience of driving through the still-dotted pump-jack landscape around town.