This souvenir sheet honors the 100th anniversary of the nine-stamp set of commemorative stamps issued in 1898 for the Trans-Mississippi Exposition, Omaha, NE. The issue came out during the Spanish-American War, which impacted both the design and release date. The stamps were intended to be bi-color, but production demands at the Bureau of Engraving and Printing required the stamps to be printed in single color. Production issues caused the stamps to be placed on sales more than two weeks after the exposition opened.