The Putnam Division was first organized in 1869 as the New York and Boston Railroad. After a series of name changes, consolidations and bankruptcies, it opened in 1881 as the New York City and Northern Railroad.
Here are some pictures of some of the structures remaining along the old railroad grade:

Elmsford station — This station is on NY Route 9A just south of NY Route 119, and is currently used as the Tony La Stazione Restaurant.

Railroad bridge at Eastview -- The entire town of Eastview was obliterated when John D. Rockefeller, Jr. had the Putnam Division relocated from his Pocantico Hills estate in 1931.

Old boxcar at Eastview — This old rusting boxcar sat forgotten on a siding at Eastview and was eventually removed in the 1980s.

Briarcliff Manor station — Walter W. Law (who built Briarcliff Lodge) donated this Tudor-style station to Briarcliff Manor in 1909. It is currently used as a library.

Millwood station — When Briarcliff Manor station was built, the old station was moved a few miles up the line to Millwood.

Railroad bridge over Croton Reservoir — Much of the Putnam Division has been paved over for use as a bike path.

Yorktown Heights station — A turntable and freight yard were located just south of the station.

Caboose at Yorktown Heights — This Penn Central caboose (PC 19123) was built in 1916. It was originally in service around Pittsburgh, and donated to Yorktown Heights in 1977. It is currently part of the Danbury Railway Museum.

Baldwin Place freight house — The station is gone, but the freight house from this station still exists.

Lincolndale station — Lincolndale Station was built in 1915 and was actually located on the Harlem Division's Mahopac Branch line, which connected with the Putnam Division near Baldwin Place. The Mahopac Branch was 7.22 miles long and carried freight and passengers from Golden's Bridge to Lake Mahopac.