These large compressor wheels were about 22 feet in diameter, weighed about 20 tons each, had 22 grooves for 1-1/2 inch rope, and carried about one-half mile of rope on each wheel. Originally installed about 1903 and operated until about 1964, the compressors ran 24 hours a day making compressed air that was piped to the mines on the Butte Hill to operate drills underground and to power hoists, which had originally been run by steam. Several other mines had similar compressor plants, but all are gone today. Lloyd Harkins saved these wheels and many other Butte historic artifacts from being scrapped when underground mining shut down.