As a wealthy international trader, John Langdon contributed his highly developed business acumen during the Revolutionary War to the problem of supplying the Continental Navy. This booklet on Langdon is one in a series on veterans of the Revolutionary War who were also signers of the U.S. Constitution, and it covers his business affairs and political activities prior to the War, his military service in a state militia company and as a state marine agent, and his public service to New Hampshire as a delegate to the Constitutional Convention, U.S. Senator, and governor. Personal data about Langdon and suggestions for further readings are also included. (DJC)