In 1898 the colors of many of the regularly issued stamps, the designs of 1894, were changed to conform with the colors assigned by the Universal Postal Union. The one-cent stamp was changed to green in January, the five-cent to blue in March and later that year, the ten-cent to brown and the fifteen-cent to olive green to avoid confusion with the lower denominations. Although the color did not change on the two-cent stamp, it was re-engraved and philatelists make a distinction between the new re-engraved type IV stamps and the earlier type III stamps.

As with the Columbian Exposition Commemoratives of 1893 and the commemorative stamps that followed in the next few decades, the Trans-Mississippi commemoratives were issued to promote an exhibition, the "Trans-Mississippi and International Exposition" held in Omaha, Nebraska from July through November 1898. To promote the exhibition, this set of stamps was issued a couple of weeks before the event began. Sometimes this issue is referred to as the "Omaha Issue" or simply the "Omahas".

The original designs called for bi-colored stamps, but the Spanish-American War had kept the Bureau of Engraving and Printing so busy producing the needed Revenue stamps, that it was decided to print the stamps in one color only. In 1998, the Bureau reissued these stamps in their original bi-colored designs.

Coming on the heels of the Columbian Commemoratives with the large number of high value stamps, in what was then considered a very brief interval between issues, there was some reluctance among collectors regarding the purchase of the high-value stamps for their collections. This fact is well manifested in the high prices the dollar stamps command today.