From 1937 through 1953, US iron ore made up more than a third of the world's iron ore production; the proportion of world iron ore mined in the US peaked in 1945 at 56 percent. Colonial. Iron mining in the United States began in 1608, when a ship returning from the Jamestown Colony in ia carried a load of iron ore back to England.
LKAB places great emphasis on refining every element of the underground mining process, in order to make it as efficient as possible. From the Kiruna mine alone, more than 75,000 tonnes of iron ore are mined per day, which is roughly equivalent to the volume of a 12storey building. You can read more about underground mining here.