Painted horses / Malcolm Brooks.

Enhanced descriptions from Syndetics:

In the mid-1950s, America was flush with prosperity and saw an unbroken line of progress clear to the horizon, while the West was still very much wild. In this ambitious, incandescent debut, Malcolm Brooks animates that time and untamed landscape, in a tale of the modern and the ancient, of love and fate, and of heritage threatened by progress.

Catherine Lemay is a young archaeologist on her way to Montana, with a huge task before her--a canyon "as deep as the devil's own appetites." Working ahead of a major dam project, she has one summer to prove nothing of historical value will be lost in the flood. From the moment she arrives, nothing is familiar--the vastness of the canyon itself mocks the contained, artifact-rich digs in post-Blitz London where she cut her teeth. And then there's John H, a former mustanger and veteran of the U.S. Army's last mounted cavalry campaign, living a fugitive life in the canyon. John H inspires Catherine to see beauty in the stark landscape, and her heart opens to more than just the vanished past. Painted Horses sends a dauntless young woman on a heroic quest, sings a love song to the horseman's vanishing way of life, and reminds us that love and ambition, tradition and the future, often make strange bedfellows. It establishes Malcolm Brooks as an extraordinary new talent.