Milford Mine stood at the northern extent of the Cuyuna Iron Range, where exploratory drilling between Island Lake and Foley Lake revealed large quantities of manganiferous iron ore. Underground development and ore extraction began in 1918 under the name Ida Mae Mine, and the ore's high manganese content was especially valued during the First World War because it produced hard, durable steel. Operations ceased in 1920, and the mine reopened in 1922 as the Milford Mine. By 1924 more than 100 people worked there in two shifts around the clock. On February 5th, 1924, forty-eight miners were working below when, about fifteen minutes before the end of the day shift, water and mud flooded into the mine so rapidly that all mining levels and the 200-foot-deep shaft filled to within fifteen feet of the surface in less than twenty minutes. Only seven miners reached the surface, making it the worst mining disaster in Minnesota history.