This stamp itself is historically significant. It inaugurated U.S. participation in the Universal Postal Union, which set a 5-cent rate (per ounce) for mail going abroad.
Zachary Taylor joined the army in 1808, rising to the rank of major. He left in 1815 but returned the following year, and for the next 16 years served at various frontiers. He was promoted to colonel in 1832 and led the First Infantry Regiment in the Black Hawk War. Taylor was promoted to brigadier general for his participation in the Seminole Wars. He was placed in command of the military department of the Southwest and moved to Baton Route, LA. President James K. Polk ordered Taylor to occupy the Republic of Texas after its annexation was approved and to defend Texas against a possible Mexican invasion.
Following failure of a U.S. peace initiative, Polk ordered Taylor south to the Rio Grande. Taylor won unexpected victories at Palo Alto and Resaca de la Palma and was promoted to major general. Then followed a series of blunders, for which Taylor was severely criticized by Polk. Polk ordered that the bulk of troops be turned over to Gen. Winfield Scott. Taylor did not take the defensive position ordered and occupied Saltillo.
Polk, attempting to arrange an armistice, allowed Mexican dictator Antonio Lopez de Santa Anna safe passage through the U.S. blockade at Veracruz. Santa Anna then attacked Taylor's position. Taylor won a surprise victory. The victory brought him wide acclaim, and the blunders largely were forgotten. Taylor's popularity propelled him past Henry Clay to the Whig nomination for the presidency, with Millard Fillmore as his running mate. Taylor won in a three-person contest, but died while in office.