The National Postal Museum, a division of the Smithsonian, is commemorating the 150th anniversary of the American Civil War with several online and physical exhibits. View the collection via this website: National Postal Museum: The Civil War: 150 years. The collection includes commemorative stamps, reproductions of civil war era stamps, a series of letters written during the Civil War, and many, many more. It’s an amazing Civil War showcases. It’s well worth a peek!