In 1840, State Geologist Douglass Houghton confirmed the presence of copper in the Upper Peninsula’s Keweenaw Peninsula—vast deposits of pure, native copper, much of it right near the surface. The U.S. acquired the western half of the U.P.—and its mineral rights—from the Ojibwa in 1842, as prospectors began flooding toward the wild and remote Keweenaw. The young country had an insatiable appetite for the metal, first for new industrial machinery, and later, for Civil War hardware, electrical wiring, and other innovations. Houghton’s find was nearly as good as gold.

The Copper Rush began almost overnight, first with prospectors, then large mining enterprises swarming the Keweenaw. Lucky prospectors secured deck space on Great Lakes vessels, sailing up Lakes Huron and Michigan, then along the southern shore of Superior. But hundreds of others straggled through the roadless wilderness, trudging overland through northern Wisconsin by snowshoe, or following rivers through thick forests to reach the fabled riches. It was the nation’s first mineral rush. Copper employed thousands of immigrant laborers, built cities, made millionaires, and prompted extravagant luxuries like opera houses and “copper baron” mansions. Before it was over, King Copper generated more than $9.6 billion—10 times more money than the California gold rush.

The entire nation turned to the Keweenaw for its copper. From 1845 to 1895, the Keweenaw Peninsula produced 75 percent of U.S. copper; during the Civil War, it produced 90 percent. More than 400 mining companies operated in the Keweenaw over the course of the 19th century, and the resulting demand for labor drew immigrants from more than 30 countries—most notably, the British Isles and Scandinavia. With multiple cultures sharing the same mine shafts and communities, the Copper Country served as one of the nation’s first true melting pots.

In the mid-1900s, however, virtually all the big mines disappeared, sealed up by economic conditions, leaving behind tattered houses and empty streets. They had extracted the easiest-to-reach copper; soon, newer mines in the southwestern U.S. and South America proved more cost-effective.