Photo from Shorpy.com , the 100-Year-Old Photo Blog. Note the guy with the pegleg.
After the jump, the 1934 London Terrace Tatler  waxes eloquent about the Cowboys and their brave ponies.
Note: This story was taken from the London Terrace Towers site, which has a great history section .
London Terrace News - January 1934
Cowboys of the Cobblestones
Law of the Range
The story of these riders goes back to December 4, 1850 when the City Council passed a law compelling trains on the streets of New York to be preceded by a rider on horseback, on block ahead of the locomotive, waving a red flag by day and a red light by night to warn pedestrians and prevent runaways of horse-drawn vehicles. This quaint law is still in force, and the New York Central must, until it rises above the street, provide its riders or suffer revocation of its franchise.
Two Mile Ride
The Tenth Avenue freight route extends from 30th Street south to St. John's yards below Canal Street, a distance of about two miles. To cover the operation of the various trains, a staff of twelve riders is maintained. These boys, who must all be over eighteen years old, are almost wholly recruited from Tenth Avenue and West Street, and strange as it may appear, riders are difficult to find, and only those who have, by strange fortune, learned to ride in the county are used, because a country boy knows and understands horses, and is thus prepared for any unexpected excitement that might affect his steed.
The "Ranch Boss" of these cowboys is the Superintendent of the New York Central Freight Yards, and since the law has been in effect two of the riders have risen from the range to the important position of Yard Masters.
The horses used in this unusual service are tried and true, and are perfectly aware of their important mission in life. They know traffic and excitement, thick fogs and blinding storms, the deep-throated adieus of departing liners and the tremendous thrill of screaming fire engines, but through it all they move surely and serenely, carrying out the Law of the City Council and giving opportunity for their gallant riders to amuse the passerby with amazing variation of the routine waving of the red lanterns. The effective term of duty of these mounts for this service is over eight years, duet to the special care and the use of rubber padding on their hoofs, and when their usefulness on the city pavements is over they are auctioned off at the Bulls Head Horse Market to continue their lives on softer turf in greener pastures.