They call it a museum, but it’s really a mine plus an ersatz mining town: The World Museum of Mining in Butte, Montana. They offer underground mine tours which we skipped. There is plenty to see without going underground.
This is the site of the Orphan Girl mine where copper and molybdenum were mined into the 1950s. There is now a huge open pit mine north of town, It’s more economical than underground mining.