Opened in May 1899, the 300 Stamp Mill was a 340 ft. long by 85 ft. wide stamp mill erected at the Alaska Treadwell mine. When built in 1899, it featured the largest number of stamps on a single ledge under one roof in the world. Each of the 300 stamps weighed about half a ton and dropped 98 times per minute. This was the first stamp mill ever built with a concrete foundation. The 300 Stamp Mill operated until the 1917 cave-in. Remnants of the foundation remain today.
“On January 11, 1898, Captain Thomas Mein, representing the Alaska-Treadwell group of mines, signed the largest contract ever executed anywhere in the world for mining machinery with Fraser & Chalmers of Chicago. The $400,000 contract was for 520 stamps – 300 of them for the Treadwell’s new mill (the 300); 120 for the Ready Bullion and 100 for the 700-Foot. The order also included compressors, winding engines, Corliss compound engines, and three hoisting engines: a Riedler air compressor, 208 Frue vanners and adjustable Comet crushers. The weight of the machinery was over six million pounds.”
-San Francisco Chronicle, January 12, 1898