Prentiss started work in the treasurer's office of a cotton mill in Massachusetts, then went to Cincinnati as treasurer of the White Water Valley railroad. In 1875, he moved to New York and began to manufacture taps, dies, and small tools, and opened a store at 14 Dey Street to sell machine tools. In time there developed a group of machine tool companies known as the -Big Six" (Cincinnati Bickford, Cincinnati Grinders, Cincinnati Milling, Cincinnati Planer, Gould & Eberhardt, and Lodge and Shipley). Prentiss represented them all, plus Blanchard, Giddings & Lewis, and others, in a territory that included, in its early days at least, the entire country. In 1893 Prentiss gave the region beyond Pirtsburgh to his Western representative, thus creating Marshall & Huschart, whose territory later divided again to create Motch & Merryweather. Prentiss continued to operate in the East until 1942, when the war brought an influx of orders that put more strain than he could take on both his personal energy (he was 95) and the capital of his firm. On March 1, 1942, the firm shut down, but Prentiss had shaped the method of machine tool distribution in the United States.