On December 3, 2016, we went to Britannia Mine for a school field trip. Grades K - 9 attended. Britannia Mine was operational from 1904 to 1974.
The mine mined mostly for copper, but also for other useful minerals. To refine all these minerals, Britannia had to make mills. They made two, but the first burned down, and the second just wasn't big enough, so they tore it down. They then made a huge third mill that took eighteen months to make by hand.