It had been requested, almost demanded, by Senate Budget Committee chairman Pete Domenici of New Mexico, and Washington Post stamp columnist Bill McAllister tells the Stamp Collecting Forum that's awfully persuasive. "The Postmasters General have to bow to the political realities of Washington, and keeping Senator Domenici happy just happens to be one of the realities "of the moment," he said.

The Postal Service brags that it doesn't receive one cent of taxpayer money to deliver the mail, but McAllister says Congress still wields a lot of power. "It doesn't get money, that's true, but it can also have money taken away from it."

Postal Service spokesman Barry Ziehl says the stamp was never ruled out. "The CSAC -- did have this stamp on the agenda," he told the Virtual Stamp Club. "They were just mulling over the different designs that were possible to celebrate this subject."

Ziehl says the delay in announcing the stamp for this year was coming up with the design. "The Committee members were working with different designs, and were struggling to get the right design that sent the right message and told the historical significance of these expeditions."