Clark’s electrically-powered mill, built in 1904, produced 100 barrels per day. The mill was located at located at West 3rd Street in Missoula.  A large storage elevator for 100,000 bushels of wheat was built alongside.  Wheat came from the Bitterroot and Drummond areas.  C. H. Richardson was appointed manager, in addition to his duties as manager of Western Lumber Company.  He paid the farmers an average of $0.75 a bushel for their wheat.  Once milled, the flour was sold under the brand names of “Missoula,” "Excelsior” and “Magnolia,” and salesmen sold the product from Deer Lodge to Sandpoint, Idaho. 

The Missoulian had nothing but praise for Clark’s mill, stating, "It has oft been remarked that if W.A. Clark has one pet institution it is the Western Montana Flouring Mill.  Mr. Clark appears to take a more keen delight in this institution, perhaps  because the product is white against a white output of most of his products…The management of the mill has been eulogized by many experts in the flour milling business and the eastern manufactures have been forced to admit that the Western Montana Flouring Mill is  putting out as good as the best flour in the world."

By 1921 flour was being produced under the name of Ravalli Flour and Cereal.  The 80-foot structure burned in 1949 but was rebuilt by 1951.  The facility was called the Montana Flour Mills Company and Feed Mill on the 1958 Sanborn Map of Missoula.