American Mutoscope and Biograph Company filmed this footage on May 21, 1905. In order to film this point of view, the company mounted a camera on the front of a subway car and followed another train on the same track, while a specially constructed work car, fitted with lights, lit the dark tunnel from a parallel track.
According to The Library of Congress :
“At the time of filming, the subway was only seven months old, having opened on October 27, 1904. The ride begins at 14th Street (Union Square) following the route of today's east side IRT, and ends at the old Grand Central Station, built by Cornelius Vanderbilt in 1869. The Grand Central Station in use today was not completed until 1913.”