There are uncountable billions of tons of big rocks out west that could be busted up into gravel to be used in road building.
Set up tent cities for them and and hand them a sledgehammer.
In Viet Nam I worked in a rock quarry for a couple of months. A ‘round’ rock will not crush, they just bounce in the crusher jaws. We’d hire older men and women to break these rocks in half. They used a one or two pound hammer and a chisel. Tap, tap, tap, tap all day long then like magic this four foot across stone would fall in two pieces. It just amazed me that they knew where to place the chisel to crack this monstrous rock.