At the time, Michigan was considered the losing party in the compromise. The land in the Upper Peninsula was described in a federal report as a "sterile region on the shores of Lake Superior destined by soil and climate to remain forever a wilderness." This belief changed when rich mineral deposits (primarily copper and iron) were discovered in the 1840s. The Upper Peninsula's mines produced more mineral wealth than the California Gold Rush, especially after shipping was improved by the opening of the Soo Locks in 1855, and docks in Marquette in 1859. The Upper Peninsula supplied 90% of America's copper by the 1860s. It was the largest supplier of iron ore by the 1890s, and production continued to a peak in the 1920s, but sharply declined shortly afterward. The last copper mine closed in 1995, although the majority of mines had closed decades before. Some iron mining continues near Marquette. The Eagle Mine, a nickel-copper mine, opened in 2014.