In 1916, O.D. Duncan and Russell T. Mount opened law offices at 27 William Street in New York City and began building a practice in admiralty and insurance law. The First World War saw the practice grow rapidly with shipbuilding disputes, financing, and claims for vessels and cargo lost at sea. In the 1920's, much of America's industrial activity was insured in the London insurance market and the firm was often retained by London insurers in defense of litigation in the U.S. In 1938, O.D. Duncan was appointed general counsel to Lloyd's, the only individual attorney to be so appointed. As World War II approached, the firm helped set up Lloyd's American Trust Fund, a $40 million reserve which ensured Lloyd's ability to meet its policy obligations in the U.S. throughout the war. In 1946, Duncan was made an honorary member of Lloyd's and after his death in 1947, the firm was renamed Mendes & Mount.
The firm's practice has always been insurance-related, from basic defense and prosecution of suits, claim program review, loss control and claim prevention, contract interpretation and drafting to regulatory counseling and financial regulations compliance and administration. Practice areas have expanded to include aerospace and satellite communications, environmental litigation, mass toxic tort and product liability. The firm is staffed largely by dual professionals--lawyer-engineers, lawyer-accountants, lawyer-aviators and lawyer-mariners.