You wouldn't see these magnificent (if dangerous) horse carriages galloping up and down Fifth Avenue much longer at the time this photo was taken. 1900 was the year that the NY State Senate approved a bill allowing the Fifth Avenue Stage to run automobiles along the length of its newly-extended route.
By 1903, the horse carriages had been retired for "motor buses."
This was a relief to the residents of the apartment blocks near the "big stable" of the Fifth Avenue Stage located uptown. The stables took up the whole block between 88th and 89th Streets, were four stories tall, and housed over 250 horses. Its neighbors were continually filing complaints with the city because of the "noxious odors", as well as perpetual stamping and neighing of horses in their stalls, which made sleep impossible.
Commentary by Louise on http://www.shorpy.com/node/8588?size=_original