Until Brower started his Broadway omnibus service in 1827, the cities of the United States (and the world) lacked dependable public transportation. Abortive attempts had been made. Blaise Pascal, just before his death in 1662, tried to set up scheduled service in Paris. Individual hackneys had been available in London. But Brower apparently found the "tipping point" in the year 1827. The world was ready. In Paris Stanislaus Baudry in 1828 revived Pascal's failed effort, and in London George Shillibeer in 1829 began service similar to Brower's. The need for such service led to its explosive growth. Photos and stereopticon views show congestion in the streets of New York City that rivals that of today. Other cities sought similar service, and the demand for such vehicles was soon worldwide. By 1856 Stephenson was producing 300 omnibuses a year. He shipped vehicles to both coasts of the U. S., to Mexico and countries in South America, to Europe, Russia, and Japan, and to Bombay, India. The success of Stephenson's omnibuses presaged in the 19th century the success in the 20th of Henry Ford's Model T's, but Stephenson's colorfully decorated vehicles would have contrasted sharply with Ford's uniformly black and undecorated ones.
Because the congestion was so bad, and because the muddy conditions of many streets could make movement of the omnibus itself difficult, the idea of putting the cars on rails became attractive. Horses continued to provide the power. New York had its first horse car line on rails in 1832. "By the 1880's there were some 525 horse car lines in 300 American cities." (George W. Hilton, Transport technology and the urban pattern," Journal of Contemporary History Vol 4, no. 3 July 1969, 123-125.)
Stephenson's familiar omnibus continued to be an ever-present part of the daily scene in cities of the U.S. and of many foreign countries. The painting "Wall Street, Half Past Two O'Clock, October 13, 1857," by James Cafferty (1819-1869) and Charles G. Rosenberg (1818-1979), shows that it also remained a significant part of the city of its birth. In the picture it stands ready as usual, door open, waiting for the next passenger.
Brower's Broadway service that had started the entire revolution in public transportation continued to serve the public until June 21, 1885, when, according to Fred Dietz, 1913: A Leaf from the Past (p. 59), his omnibuses were "superseded by Horse Cars" on rails. John H. White, in his Horsecars, Cable Cars and Omnibuses (p. xi) says that Stephenson's shop appears to have continued limited omnibus production until the late 1890's" and that "New York's horse-drawn buses ran as late as 1908." And the New York Transit Museum's website (see Bibliography) informs us that it was 1917 before "Manhattan's last horsecar line [on rails] stopped running on Bleecker Street."
By the first years of the new century downtown streets of urban America were a jumble of vehicles. In this image of Boston's Post Office Square in 1904 I cannot find that any motorized vehicle has yet joined the confusion (see Bibliography).