I had an opportunity to see the exhibit – Freedom Just Around the Corner- at the National Postal Museum. Nice to see items on the Smithsonian website.
“U.S. postage stamps were in use for nearly a century before Booker T. Washington became the first African American to appear on one. A handful of additional black history-related designs appeared between 1940 and 1978, when the U.S. Postal Service introduced the Black Heritage series. Today the Black Heritage issues are the longest-running U.S. stamp series”