William Ladd (1778-1841) suggested in the 1820s to the Maine Peace Society that the regional peace societies, which had grown up in the United States since 1815, become associated in a national organization. As a result, the peace societies of Maine, New Hampshire, Massachusetts, New York, and Pennsylvania (Philadelphia) merged in May 1828 to form the American Peace Society [APS]. Most local societies also became affiliated, with varying degrees of control from the national office. The political philosophy of the APS was never as radical or pacifist as some reformists would have liked, so some activists broke away to form new organizations, such as the New England Non-Resistance Society in the 1830s, and the Universal Peace Union in 1866. The stated purpose of the American Peace Society was to "promote permanent international peace through justice; and to advance in every proper way the general use of conciliation, arbitration, judicial methods, and other peaceful means of avoiding and adjusting differences among nations, to the end that right shall rule might in a law-governed world."
William Ladd was one of the first to propose a Congress of Nations and a World Court. The APS was instrumental in bringing about many peace congresses at The Hague, beginning in 1843, and in the United States in 1907-1915, as well as the Pan American Congress, out of which grew the Pan American Union.
The APS published Harbinger of Peace, The Calumet, Advocate of Peace, A.P.S. Bulletin, and World Affairs Bulletin. It also published many pamphlets and books to "mold public opinion in this country and abroad on the subject of international friendship" and peace.
The headquarters of the Society moved in 1835 from Hartford, Connecticut to Boston, Massachusetts, and in 1911 to Washington, D.C., where it still has offices today (2009)