Rock Springs, Wyo. traces its origins to a coal mine established there in 1868 to serve the still-building Union Pacific Railroad. Ever since, the town has been enriched by the people who came from around the world to live and work there—in coal mines, on the railroad and, in recent decades, in trona mines to the west and the oil and natural-gas fields to the north. Rock Springs boasted 56 nationalities by the 1920s. Its political and economic fortunes have closely followed all these industries’ cycles of boom and bust.