Winslow was also the chief executive officer of the Watertown Fire Insurance Company, and he was a shareholder of the Davis Sewing Machine Company. The Watertown Spring Wagon Company was started because of him. He was a member of the New York State Senate (18th D.) from 1870 to 1873, in the 93rd, 94th, 95th and 96th New York State Legislatures as a Republican. He was a special agent in the U.S. Treasury Department from 1882 to 1890, but he quit because he was ill.