Mr. McDuffee's personal interests in manufacturing were also in the Great Falls Manufacturing Company, in whose great business he was a director for four years; capital, one million five hundred thousand dollars. In 1862 he bought large interests in the Cocheco Manufacturing Company, and has there remained. Since 1874 he has been a director of that corporation. As such, he advocated the erection of the great mill, now No. 1, and the replacing of all the old buildings by new and magnificent mills, unsurpassed in the United States,--a work now rapidly progressing. The remarkable success of this company certifies alike to the sagacious boldness and the considerate policy of its directors. The need of railroad facilities at Rochester was early apparent to Mr. McDuffee. In 1846 he entered into two enterprises,--the Cochecho road, from Dover to Alton Bay, and the Conway road, from Great Falls to Conway. Each was to and did pass through Rochester. In each road Mr. McDuffee was the largest individual stockholder, and of each was the first treasurer. When the Conway road reached Rochester, Mr. McDuffee resigned its treasurership. The other road, after various difficulties, became the Dover & Winnipesaukee, by the incorporation of the bondholders, and Mr. McDuffee continued to be a director. With "friend" William Hill, he visited Boston more than thirty times to treat for the lease of this road to the Boston & Maine. The effort was finally successful, and the road, by itself weak, became a fine piece of property. Rochester was thus doubly accommodated; but another avenue was needed, and Mr. McDuffee took part in the Portland & Rochester, which secured a route eastward, of which road he was a director; and he invested liberally in the Rochester & Nashua, which opened a line to the West. The result has been that Rochester is a "billing-point," and its various manufacturing interests have felt its impetus. The beauty of "McDuffee block" in Rochester, built by him in 1868, exhibits the owner's public spirit. It is an elegant brick building of four stories, containing six stores, twelve offices in the second story, a public hall in the third, and a Masonic hall, one of the finest in the state, in the fourth. In the use of the public hall the liberality of its owner to benevolent objects is well known. As a Mason, he joined Humane Lodge on the very day he became "of lawful age." Of other real estate, Mr. McDuffee has, besides various pieces in Rochester, including such as the Gonic farm, the New Durham "powder-mill" estate of nine hundred acres of land and eleven hundred acres of water; and in Barrington, two hundred acres on Isinglass river, held with a view to future manufacturing needs.