The first issue of U.S. stamps in the 20th century was in honor of the Pan-American Exposition in Buffalo in 1901. The 6 stamps following transportation themes were attractive, two-color engraved stamps printed by the Bureau of Engraving and Printing. It was the first two color issue after the 1869 pictorials. Search for these Pan-Americans. President William McKinley was assassinated at the Exposition on September 6, 1901. Here is more about the Pan American Exposition in Buffalo in 1901.
Although World War I was the dominant event of this decade, it was dismissed by a United States which wanted no foreign entanglements during its early years. The United States was busy planning and conducting the Panama-Pacific Exposition of 1915 in San Diego. Great Britain still was convinced that Britannia Rules the Waves! Austria's Emperor Franz Josef celebrated his 80th birthday in 1910. The first airmail stamps were some rather undistinguished Italian overprints issued in 1917. In 1918 the United States issued its First Airmails.
This was a decade which began with the aftermath of World War I which had totally disrupted the economies and boundaries of Europe. The League of Nations was formed in an attempt to deal with the problems. New nations such as Czechoslovakia arose from the restructuring of Miidle Europe. Reparations imposed by the victors including the auction of the fabulous collection of Count Ferrary brought Germany to its economic knees. Germany faced a crisis during the disastrous inflation of 1923 when stamps as large as 500 billion marks were issued. The airmail service matured with new routes being started each week at the end of decade. Envelopes flown on the inaugural flights on United States Contract and Foreign Air Mail routes were pursued.
The 1930s were a golden age for philatelists. President Franklin D. Roosevelt was an active stamp collector and provided continuous publicity for the hobby. King George V was a collector as well. Stamp collecting was rightfully known as "the hobby of kings." Some of the interesting stamps of the era were "Farley's Follies" -- stamps which were reprinted to provide protesting collectors access to some imperforate, ungummed stamps which had been given as favors to friends of the Postmaster General, James Farley. The British Commonwealth also had a heyday for stamp collecting with omnibus issues for 249 commemoratives issued in honor of the Silver Jubilee of King George V's reign in 1935. The Commonwealth issued 202 different stamps two years later for the Coronation of Queen Elizabeth and King George VI.
The United States began the decade by issuing 35 stamps honoring Famous Americans. Soon, World War II and its aftermath left its mark on stamp collecting. As is often the case, stamps were part of the propaganda of the belligerents and the tide of war made many opportunities for postal history items. The United States issued a series of 13 stamps honoring Overrun Countries which had been conquered by the Axis powers. At the conclusion of the war, the British Commonwealth again issued an omnibus issue of 164 stamps to celebrate Peace.
The United Nations began issuing stamps on October 24, 1951. The stamps are generally attractive and follow UN themes. The UN subsequently issued stamps from its offices in Geneva, Switzerland, and Vienna, Austria.
Tonga made a splash in the 1960s by introducing die-cut, shaped, foil stamps with pressure sensitive adhesive.
During the 1970s, folders containing all the stamps issued during the year became a popular marketing tool for philatelic agencies throughout the world. It was an easy way to collect the stamps issued during the year. Oftentimes the folders included pages which described the stamps and permitted them to be mounted.
The 1980s got off to a good start with the sale of the first single philatelic item to sell for $1 million. The so-called "Blue Alexandria" cover bearing a copy of the Alexandria, VA, postmaster's provisional brought the record price in a sale by David Feldman Ltd., in Geneva, Switzerland, on May 8, 1981. Stampless covers are similar interesting philatelic items from the era just before stamps became required. A new United States definitive issue honoring Great Americans was introduced during the first half of the decade. The United States Post Office Department also introduced Express and Priority Mail premium services which used high value stamps.
1992 provided the opportunity to honor the 500th Anniversary of the Voyages of Columbus in stamps and souvenir sheets. As is the case in so many things, the United States stamps followed pop culture with stamps honoring Comic Strip Classics; caricatures of Silver Screen Stars; and Legends of the West. A review of the Scott Specialized Catalogue of U.S. Stamps will reveal stamps for all tastes. In 1995, eBay went on line and grew quickly to offer over 50,000 lots of stamps for collectors.