English: habitational name from any of various places, for example in Devon, Dorset, Essex, Kent, and Warwickshire, so named from Old English lang, long ‘long’ + dūn ‘hill’.
FOREBEARS Samuel Langdon, Harvard College president in 1774–80, was born in Boston, MA, in 1723 but lived out his years in Hampton Falls, NH. Three of his children left descendants. His grandfather Philip (b. 1646) had came from Braunton in Devon, England, and was married in Andover, Essex Co., MA, in 1684, according to family historians. Another early Langdon immigrant was Tobias Langdon, who came to America before 1660 and settled in Portsmouth, NH. His great-grandson John was a revolutionary war leader, U.S.senator, and NH governor.