Discontinued post office
A discontinued post office or DPO is an American postal term for a post office which has been discontinued. Some are in ghost towns, some victims of consolidation of mail service as small post offices are closed or a city expands. The introduction of Rural Free Delivery, RFD, in 1902 led to the closure of many post offices, which peaked in 1901 at 76,945. In the United States, which was mostly rural, mail previously had been picked up in rural areas at small local post offices, home delivery being limited to urban areas until experimentation with rural delivery began in 1890.
Covers, that is letters, wrappers, or postmarks from discontinued post officers are of interest to students of postal history. As one example, in Saguache County, Colorado there are over 50 discontinued post offices.