One central characteristic of the Model T now generally forgotten is that it was the first car of consequence to put the driver's seat on the left hand side. Previously, nearly all manufacturers placed the driver on the outer, curb-side of the car so that an alighting driver could step out onto a grassy verge or dry sidewalk rather than into the mud of an unpaved road. Ford reasoned that this convenience might be better appreciated by the lady of the house, and so arranged seating for her benefit. The arrangement also gave the driver a better view down the road, and made it easier for passing drivers to stop and have a conversation out facing windows. Ford was no great thinker, but he did understand human nature. Such, in any case, was the popularity of Ford's seating plan for the Model T that it soon became the standard adopted by all cars.
-Bill Bryson, One Summer: America, 1927