51st state
Guam (formally the Territory of Guam) is an unincorporated and organized territory of the United States. Located in the western Pacific Ocean, Guam is one of five American territories with an established civilian government.
Postage stamps and postal history of Guam
When the United States Post Office Department (USPOD) took charge of the postal service of Guam in March 1901, the local population, soldiers from the US Navy base and indigenous Chamorros, had to use US stamps without any distinctive marks. Since 1901, only a Guam town cancellation indicates domestic posting. This situation is common to others insular unincorporated territories of the United States, such as, Northern Mariana Islands since 1944, Virgin Islands since 1917, Puerto Rico since 1900 and American Samoa since 1899. The existence of a local post at the beginning of the 1930s and the Japan occupation periods were exceptions.