[MorrisMcD]

Did the United States ever drive on the left?
Yes. The evidence we have been able to collect is mostly indirect, but it seems almost certain that in the early years of English colonization of North America, English driving customs were followed and the colonies drove on the left, gradually changing to right-hand driving after independence. Kincaid quotes an English author writing in 1806 as saying, "in some parts of the United States, it is a custom among the people to drive on the right side of the road," implying that in other parts, people still drove on the left. We also know for certain that the colonies farther north along the coast drove on the left well into the 20th century (see the question about Canada below). I have read that the first law requiring drivers to keep right was passed in Pennsylvania in 1792, and that similar laws were passed in New York in 1804 and New Jersey in 1813, but I don't yet have primary sources for this information so it is possible that these states weren't changing sides, but only codifying existing practices in law. Other anecdotes from various sources also support the conclusion that most states drove on the left until some time in the early 1800s. American cars had their steering wheels on the right (the best arrangement for driving on the left-hand side of the road) until the early 1900s (see the discussion of this below).

However, Kincaid is not convinced that left-hand driving was ever widespread in the American colonies. He points out that the colonists were not exclusively English (for example, the Dutch settlers of New Amsterdam, which later became New York, would have been accustomed to driving on the right), and says that the first vehicles used by the colonists were carts and postilion-control wagons such as the Conestoga, which are best driven on the right. Wagons like the stagecoach (best driven on the left) were not introduced until much later -- too late to change the established practice.

http://www.brianlucas.ca/roadside/