On December 12, 1928, the Post Office Department issued 2-cent and 5-cent stamps in celebration of the International Civil Aeronautics Conference. Held in Washington, D.C. from December 12-14, 1928, the conference marked the twenty-fifth anniversary of the Wright Brothers' successful manned flight at Kitty Hawk. The stamps were notable for the following reasons:
• They represent the first time the Post Office celebrated the Wright Brothers' achievements;
• They were issued from a non-postal facility, a rare occurrence for 1928; and
• The first day cancellations were applied in green, the first time non-black ink was used for first day postmarks by machine.
The United States was eager to assume a leadership role in international aviation policy and industry growth. This led President Calvin Coolidge to suggest an international conference in Washington, D.C. Congress appropriated funds, and the State Department issued an international call for papers to those countries with which the United States had diplomatic relations. However, the Commerce Department assumed oversight of the conference during its presence in Washington. Herbert Hoover, then-Secretary of Commerce, was an avid stamp collector.