U.S. Postal Service
01-01-2004
Meriwether Lewis and William Clark stamps from Summer 2004, accompanied by a commemorative print titled "Lewis & Clark: The Corps of Discovery."
http://digitalcommons.wku.edu/scl_broadsides/189
https://digitalcommons.wku.edu/context/scl_broadsides/article/1181/type/native/viewcontent