The development of the "ubiquitous gasoline engine", and the parallel development of petroleum, was the key required to unlock the door to personal vehicles. We could have conceivably gone with electric propulsion, but electricity didn't become widespread until the late 1800's and it was generally in an inconvenient form for recharging slow, heavy, and quick-to-run-down battery powered cars. The light, speedy, indefatigable, and ultimately cheap gas motor won the day. Throughout the 19th century, occasional experimenters demonstrated steam-powered carriages or "road locomotives" but the skills and attention required to manage a steam engine were unrealistic for a solo driver, and the roads were dreadful due to travel being diverted to railroads. Large bridges were built to carry railroads, street car lines, and a smattering of foot and horse traffic.

[Steam-powered automobiles (Dobie, Stanley etc.) attained a certain measure of popularity. In the final years of the 19th century, the Stanley brothers' steam-powered vehicle was America's top-selling motor car. The company they founded lasted a quarter of a century. - Dave]

Cool, I'll give you a call once my Nigerian money comes through.

Only paid $500, and I've got the title to prove it.

Each time a see a circa 1900 urban scene on Shorpy, I ponder how technology was so slow in developing the automobile in comparison to the other machines and structures in existence at the time. I am alway struck by the incongruity of large urban buildings surrounded by horse drawn wagons. This picture really drives the point home. Let us not forget that the unseen traffic crossing this magnificent bridge at its opening was mostly horse-drawn or pedestrian. The big boats in the water were steam powered. The age of the ubiquitous gasoline engine was yet to come.