In 1847 railroads carried only about 10 percent of the U.S. mail while the remainder was transported by steamboat, by stagecoach, and on horseback. In 1855 the railroads began using special mail cars and central distribution points. By the 1870s the U.S. Postal Service was the largest and one of the best in the world even though it was irregularly administered.

Urban Free Delivery.

Before 1825 there was no home delivery service. In that year the postmaster general was authorized to begin delivery in cities with populations of more than ten thousand. A carrier was not paid a salary and depended on collecting a one- or two-cent fee from the recipient, an awkward arrangement for everyone involved. This system lasted until 1863, when in the midst of the Civil War, Congress deemed that the carriers should be paid by the government. Other reforms soon followed. In...