Q: Who is responsible for all those mines?

Many of the old mines were worked in the late 1800's through the 1940's. When the mines played out, or the market for metals got bad, the miners simply walked away in search of richer finds elsewhere. Even on mines that were patented (sold to the miner by the government) the original owners are long dead. Their descendents often don't know what they own or the mine has been sold for taxes or repossessed by the state.