“Utah was dubbed ‘The Uranium Capitol of the World.’ Between the years of 1946 and 1959, there were 309,380 claims of uranium found in Utah, and by 1955, there were about 800 operating mines.”
https://www.intermountainhistories.org/items/show/646
a more detailed article:
https://www.uen.org/utah_history_encyclopedia/u/URANIUM_MINING.shtml