The Mesabi Range's iron ore formed during the middle Precambrian period, when erosion from ancient mountains released iron and silica into a newly formed sea. Marine algae raised atmospheric oxygen in what geologists call the Great Oxidation Event, causing the iron to precipitate into banded iron formations now grouped in the Animikie Group. The result is the Biwabik Iron Formation, a cherty layer bearing both natural hematite-goethite ores (51 to 57 percent iron) and magnetite taconites (30 to 35 percent iron, beneficiated to pellets of 60 to 67 percent). The range is a monocline dipping 5 to 15 degrees southeast, extending from Babbitt in the northeast to Grand Rapids in the southwest. Key faults -- the Calumet, La Rue, Morton, Biwabik, and Siphon -- break up the formation, while the Duluth Gabbro complex to the east has caused metamorphic changes in the ore body. Pike Mountain, the highest point, rises northeast of Virginia.

Iron ore was discovered north of Mountain Iron on November 16, 1890, by J. A. Nichols working for the Merritt brothers, a family of prospectors from Duluth. By 1892, mining was underway. But the Mesabi's soft, powdery ore was a problem: American steel furnaces were not built to process it, and steelmakers dismissed it as poor quality. John D. Rockefeller saw opportunity where others saw dust. He invested $40 million to build up the Mesabi ore and transportation business, including $2 million for a railroad to Duluth. By 1896, he controlled the Lake Superior Consolidated Iron Mines Company. He struck a deal with Henry W. Oliver and Andrew Carnegie: they would stay out of ore and transportation, he would stay out of steel. When Oliver broke the agreement, Rockefeller responded by monopolizing ore ship transportation on the Great Lakes. In 1901, he sold his holdings to J. P. Morgan for $90.9 million -- part of the consolidation that created United States Steel.

Initially, underground mines worked the Mesabi ore, but the deposits lay so close to the surface that open-pit mining quickly dominated. By 1902, half the operations used open pits. The last underground mine closed in 1960. Five-ton steam shovels carved enormous terraces into the earth, creating pits visible from orbit. The Hull-Rust-Mahoning mine in Hibbing became the world's largest open-pit iron mine. The men who worked these pits came from Finland, Italy, Slovenia, Norway, Sweden, and Germany, and they brought with them traditions of labor organizing. On July 20, 1907, the Western Federation of Miners struck the Oliver Iron Mining Company, demanding an eight-hour workday and a pay raise. The strike lasted two months and ended with thousands of workers blacklisted. On June 25, 1916, a single miner walked off his shift after being underpaid, sparking a broader strike backed by the Industrial Workers of the World. The workers voted to return in September, believing they had failed -- only to receive a 10 percent raise shortly after.

By the mid-20th century, the high-grade direct-shipping ores that had made the Mesabi famous were running out. The region's survival depended on learning to process taconite, a harder, lower-grade ore that required crushing, concentrating, and pelletizing before it could be used in blast furnaces. The transition reshaped the entire industry. Today, six mining-processing facilities operate on the range. Cleveland-Cliffs runs Northshore Mining in Babbitt and Silver Bay, plus United Taconite with operations in Eveleth and Forbes. ArcelorMittal operates the Minorca Mine near Biwabik and Gilbert. United States Steel runs both KeeTac in Keewatin and Minntac in Mountain Iron. Hibbing Taconite operates between Hibbing and Chisholm. The mined ore travels by Canadian National Railway to the ports of Two Harbors and Duluth, and by BNSF Railway to Superior, Wisconsin, where trains of up to eighty 100-ton cars dump their loads into lake freighters carrying 60,000 tons to steel mills in Indiana and Ohio.

The Mesabi Range today is a landscape of contrasts: active taconite operations alongside exhausted pits filling with groundwater, turning into lakes ringed by birch and pine. The Minnesota Discovery Center in Chisholm, the Hull-Rust Mine View in Hibbing, and the 145-mile Mesabi Trail draw visitors interested in mining heritage and the boreal landscape. Former mine lands are being redeveloped -- the Rock Ridge Public Schools campus in Virginia sits on a reclaimed mining site, and the Virginia Pilot housing project is converting old mine grounds into residential space. But the Iron Range faces the demographic headwinds common to rural Upper Midwest communities: an aging population, youth outmigration, and overall population decline. The region's strong ties to its labor and immigrant history persist in ethnic festivals, historical societies, and the annual Iron Range Labor Day Picnic. The giant holes in the earth remain, both scars and monuments to the ore that built a nation's industrial backbone.