The breadth of U.S. postage stamps issued during the 20th century is staggering, from denominational postage bearing formal presidential portraits to stamps that celebrate everything from national parks to space exploration. In general, unused stamps are more expensive to collect than used stamps, which makes condition an important determinant of a stamp’s price.
One of the most collected series was issued early in the century, on May 1, 1901, to promote the Pan American Exposition and World's Fair in Buffalo, New York. Issued in denominations of 1, 2, 4, 5, 8, and 10 cents, the stamps show off America’s transportation know-how, from steamships to trains to automobiles. Another early series, this one produced to promote the St. Louis World’s Fair, celebrated the centennial of the Louisiana Purchase. Images in this series include the 10-cent stamp, which features the boundaries of the Louisiana Purchase overlaid on a map of the United States.
The U.S. Air Mail stamps of 1918 are noteworthy because one sheet of the first release, with a denomination of 24-cents and the image of a Curtiss Jenny biplane on its front, was printed with the biplane upside down. Subsequent airmail stamps from 1918 saw denomination decreases to 16 cents and then just 6 cents. In 1930, images of Graf Zeppelins were printed on 65-cent, $1.30, and $2.60 stamps (a “Baby” Zeppelin stamp was also issued in 1933).
Ten National Parks stamps, in denominations from a penny to a dime, were issued in 1934, and numerous commemoratives were issued in 1937 (Union generals Sherman, Grant, and Sheridan got a 3-cent stamp, while Confederate generals Lee and Jackson were remembered on a 4-cent stamp). In 1940, Famous Americans were given stamps, organized by authors such as Irving and Twain, poets like Longfellow and Whitman, and inventors such as Morse and Bell (in all, 35 Americans were thus honored).
During World War II, the 13 Overrun Nations stamps issued in 1943 and ’44 are noteworthy because they marked the first time the Bureau of Engraving and Printing (BEP) contracted work to an outside printer (American Bank Note). In addition, instead of plate-block numbers, the sheets were printed with the name of each occupied nation. Later that decade, in 1947, the Postal System marked its own centennial with a souvenir sheet showing the first two U.S. stamps, a 5-cent Franklin and a 10-cent Washington. And a slew of commemoratives followed in 1948, honoring constituents as diverse as Swedish pioneers and the American poultry industry.
Stamps got more colorful in 1956 thanks to the purchase of a Giori Press, which allowed the BEP to print three colors from the same plate. Examples of Giori stamps include the Whooping Crane stamp of 1957, the International Geophysical Year stamp of 1958, the Soil Conservation stamp of 1959, and the American Credo issues of 1960 and ’61. And in 1960, the Postal Service issued the first of many space-exploration themed stamps, beginning with the 4-cent Echo 1 stamp and culminating for many collectors with the 10-cent, horizontal Giori marking Neil Armstrong’s first steps on the moon.