Seyfried (1918-2012) was an American historian of Long Island.
His work between 1950 and 2010 includes eleven books on trolley systems in Queens and Long Island, twelve books on areas of Queens, a seven-volume set on the Long Island Rail Road, and a history of the founding of Garden City, where he was Village Historian from 1987 to 2006.
He provided many entries on Queens history for The Encyclopedia of New York City (1995).