Harlem River Branch

I have NH public timetables for 1896 and 1905 that clearly show the New Haven's Harlem River Branch New Rochelle locals operating all the way to the 129th Street 2nd Ave. el station on Manhattan. Does anyone know when this started and when it ended (I'm guessing 1905/06 for the end) ?
I also recall reading somewhere that the 2nd Ave el trains ran over the NH to a race track somewhere in the southeast Bronx. Does anyone know anything about this ? Thanks in advance for any help that you can provide.

Morris Park Race Track (1889-1903) may be the track in question. It burned to the ground in 1910, after its days as a horse track were over. By then, it had been annexed by NYC and used for auto races and other events.

The direct service over the El to 129th St. in Manhattan operated from 8/1/91 to 5/11/05. During that time the service primarily originated in New Rochelle, but I'm told that some rush hour trips operated to/from Port Chester. The NH got 10 0-4-4T Forneys in 1891-92 along with wood coaches built to El dimensions.

When the direct service to 129th St. ended, the IRT inaugurated a shuttle service between the NH Harlem River terminal and 129th St. to maintain the connection with the 2nd and 3rd Ave. El lines. The NY, Westchester & Boston began using the Harlem River terminal in 1912, and also served NH stations at Westchester Ave., HuntsPoint, Casanova, and Morris Park. The shuttle was discontinued in 1924, when a new NYW&B-NH terminal was built west of Willis Ave. with a walkway to the 133rd St. (Bronx) express station of the 3rd Ave. El. NH's New Rochelle-Harlem River "suburban" service continued to operate in steadily diminishing form until 1930. In the interim, the NH bought four AC-only m.u. cars in 1915 to operated this service. The NYW&B continued to serve the four NH local stations noted until it was abandoned at the end of 1937.

And yes, special were run for the Morris Park race track. Can't tell you the dates, though.

Thanks for the help...this is very useful info. The last steam power on the 2nd Ave. el ran on Sept. 2, 1902 which sets the last date the el could have run race track specials. The USGS Harlem (NY) topo quad map (dated 1898) clearly shows the large race track as well as the NH / el spur leading to the track.