Fourth-class post office

A fourth-class post office in the United States, from 1864 to the 1970s, was a post office at which the postmaster received the lowest tier of annual commission income from postage stamps. Prior to the early 20th century, fourth-class post offices were the backbone of the U.S. postal system. They were also in many cases the backbones of the hamlets and rural communities where they were located, as they provided a local gathering place and center of civic activity. These small rural post offices followed an agency model, in which the Post Office Department used existing buildings and businesses and paid its postmasters on a commission basis.

The rise of rural free delivery and the resulting consolidation of post offices spelled the end for many fourth-class post offices. In 1901, fourth-class post offices numbered over 70,000, more than 90% of all post offices in the country. By the 1970s they numbered less than 6,000.