In Mercer County's earliest days, its proximity to New Amsterdam brought explorers and settlers. They arrived by boat, on the Delaware River, or overland on Indian trails. These trails were gradually widened, and although often impassable during certain seasons, they enabled the flow of commerce and news to continue steadily throughout most of the year.
The first stagecoach run began in 1723, and by 1738 a regular line was in operation, connecting New Brunswick and Trenton. The stage ran only in the summer, fall and winter. In 1838, the Delaware and Raritan Canal was built, and this increased trade considerably. Mule-drawn barges carried coal and other freight, and it helped bring prosperity to Mercer County for many years.
At the same time, the Camden and Amboy Railroad was built. The tracks were placed along the banks of the canal, and they connected Trenton and New Brunswick. Historians have suggested that the canal and the railroad were largely responsible for Mercer County's prosperity, and that they are still contributing to it. This is because they brought industrial and commercial power into the county, and since they were both kept out of the center of Princeton, it enabled the town to preserve its "exclusive residential character." Perhaps this factor, coupled with the university, helped create the image that the name Princeton exudes: an image that is continually attracting new businesses to Mercer County's booming Route One Corridor, and its surrounding areas.