
Given the following passage

"In 1899, the local postage stamps were overprinted "Guam" as was done for the other former Spanish colonies, but this was discontinued shortly thereafter and regular U.S. postage stamps have been used ever since. Because Guam is also part of the U.S. Postal System (postal abbreviation: GU, ZIP code range: 96910–96932), mail to Guam from the U.S. mainland is considered domestic and no additional charges are required. Private shipping companies, such as FedEx, UPS, and DHL, however, have no obligation to do so, and do not regard Guam as domestic.",

answer the following question. Note that the answer is present within the text.

Question: Why would a person in Minnesota have the same kind of postage markings on a letter as a person in Guam? 

local postage stamps were overprinted "Guam" as was done for the other former Spanish colonies, but this was discontinued shortly thereafter
