Not to be outdone, yet another McCaskill brother jumped into the milling business. At the age of twenty, John C. McCaskill entered the mercantile business in Eminence at the age of 27, and later teamed up with brother George in the mercantile and milling trade. John McCaskill became president of the McCaskill Mercantile and Lumber Company in 1881. He would go on to erect mills at Shawnee Creek (a tributary of the Jacks Fork River near Eminence) and has been credited with construction of some twenty or so mills in that area. John also owned a mercantile at Bartlett, which lies south of Alley Spring on what is now U.S. Highway 60.
One of the mills was located in Houston, Missouri and was where the father of Senator Clair McCaskill worked.