In 1999, the United States Mint struck Sacagawea Dollars in 22-karat gold. These coins carried the 2000 date and “W” mint mark, although they were actually produced in Philadelphia. Each was struck in proof format on the same 27 mm planchets used for one-half ounce American Gold Eagles. Of the 39 pieces produced, the 12 best strikes were retained and the remaining pieces destroyed. The Mint had planned to sell similar coins to the public, but plans were halted when the legal authority to strike the coins was questioned.
The 12 surviving pieces did serve a special purpose. On July 23, 1999, the 22-Karat Gold Sacagawea Dollars were launched into space aboard the Space Shuttle Columbia and travelled nearly two million miles as the shuttle orbited Earth. Following the return of the shuttle, the coins were transferred to secure storage at Fort Knox. These historic pieces would be displayed publicly for the first and only time in August 2007 at the American Numismatic Association World’s Fair of Money in Milwaukee, Wisconsin. After that the coins were returned to storage at Fort Knox.