Not since 1938 had a series of U.S. stamps been devoted entirely to past U.S. Presidents. And with this series, another postal “first” occurred when four “mini sheets” were issued by the U.S. Postal Service. Each sheet incorporated nine 22-cent commemorative stamps. Each of 35 stamps honors a deceased U.S. President, and the 36th stamp depicts the White House. These were the very first “mini-sheets” ever issued by the United States. And in addition to a President's portrait, each stamp bears a facsimile of the President's signature, plus the years he served in office.