The Third and Amsterdam Avenues Line, also known as the Third Avenue Line, is a public transit line in Manhattan, New York City, United States, running mostly along Third Avenue, 125th Street, and Amsterdam Avenue from Lower Manhattan to Fort George in Washington Heights. Originally a streetcar line, it is now the M101 bus, operated by the Manhattan and Bronx Surface Transit Operating Authority out of the 100th Street Bus Depot. The M101 bus now runs southbound on Lexington Avenue rather than Third Avenue north of 24th Street.