Hull-Rust Mahoning Mine Pit Overlook – Hibbing, MN - Minnesota Historical Markers on Waymarking.com

This marker tells about the history of the “Largest Open Pit Mine in the World.” It is located on the edge of the mine near the visitor center. Its text reads:

Immediately to the north and extending approximately 3½ miles east to west is the open pit known as the Hull-Rust Mahoning Mine, begun in 1895. In fact, over the past 100 years of mining here, more than thirty separate mining companies have operated within its perimeter, many at the same time. At one time this was known as "The Largest Open Pit Mine in the World". The mine, at its maximum depth, is 600 feet in the Scranton Pit, just below and to the west of this point.

At the beginning of this millennium nearly 2 billion tons of iron ore and waste were removed from this man made excavation. This volume is equivalent to digging a tunnel 24 feet in diameter completely through the earth. Average iron content of the ore shipped was over 60% iron with little, if any, processing of the ore required.

The largest year of production was 1942, during World War II, when more than 27 millions tons of ore were shipped during the normal nine month summer season. This required one train car of ore leaving the mine every 20 seconds for it's 90-mile journey to ore docks at the head of Lake Superior. In the 1940's more than 70 miles of rail line were used within the mine.

In 1976 Hibbing Taconite Company (Cliffs Inc.) began 'taconite' mining near the continental divide just north of the Hull-Rust Mahoning. Mining of the higher grade, and hematite rich, 'natural ores' ended in 1984. Taconite mining requires a sophisticated plant to magnetically concentrate the lower grade (30-35% iron) primary ore, upgrading it to over 66% iron and producing a final product of 3/8" furnace fired pellets. Taconite pellets are now the final product that is rail shipped to the Duluth-Superior harbor and then transferred to the Great Lakes iron ore boats for shipment to the blast furnaces.

Rain water and ground seepage at one point caused the water level in the mine to reach a maximum of over 325 feet. Subsequent pumping has brought this water level down to allow for present mining of the deeper taconite ores, as you can see below you.

- In Partnership with the Cleveland-Cliffs Foundation -

Marker Type:: Other

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