On October 9, 1874, the Universal Postal Union was formed in Bern, Switzerland where it is headquartered today. The UPU is the governing body responsible for regulations and standards regarding the passage of mail among member nations and states. The UPU currently has 192 members.
Before the Universal Postal Union, specific agreements between nations were necessary to allow the passage of mail from one country into another. After standardizing flat rate international postage, mail no longer needed to carry postage stamps from each country through which it passed. The Universal Postal Union makes it possible that the postage of one member nations is universally accepted by all other member nations. The UPU also standardized the usage of numbers for postage denominations and colors for postage types.