1899 5c Ulysses S, Grant, Blue, Porto Rico Overprint in Black

This stamp was created by overprinting an existing United States postage stamp featuring Ulysses S. Grant for use in Puerto Rico following the Spanish American War. Puerto Rico was ceded by Spain to the United States under the Treaty of Paris in December 1898, and an independent postal service under American authority was established on the island beginning March 15, 1899. During this period, the territory's English name was rendered as "Porto Rico," the spelling that appears on this stamp's overprint, a convention that remained in official use until it was formally changed to "Puerto Rico" in 1932.

The overprint reads "Porto Rico" diagonally across the design, repurposing the stamp's original five cent United States denomination for use on the island rather than converting it to a separate local currency, since Puerto Rico's postal system operated on the same denomination structure as the mainland. This overprinted issue was one of ten United States stamps overprinted for use in Puerto Rico between 1899 and 1900, filling the gap left after Spanish colonial stamps were phased out but before the island was more fully absorbed into the regular United States postal system.

That fuller integration came with the Foraker Act of 1900, which folded Puerto Rico's postal service directly into the United States postal system rather than keeping it as a separate territorial adjunct. From that point forward, regular United States stamps were used on the island without the need for special overprints.