Thornwood is an unincorporated hamlet and census-designated place (CDP) located in the town of Mount Pleasant in Westchester County, New York. The population was 5,980 at the 2000 census.
Thornwood once had a large and thriving marble quarry near its heart, the intersection of Route 141 and Kensico Road (known as Four Corners). The quarry pit was filled in in the mid 1980s and the Town Center shopping center constructed over it.
Thornwood once had a station on the Harlem Line of the Metro-North Railroad and was about a 48-minute ride to Grand Central Terminal. The station building remains on Commerce Street, but the stop was eliminated when the upper Harlem Line (north of North White Plains) was electrified in the mid-1980s. Thornwood was the only stop eliminated as a result of the electrification process. While the station could accommodate diesel trains, the curvature of the tracks as proceeding north to Pleasantville made the construction at Thornwood of an elevated platform, necessary for electric trains, impractical.