The Smithsonian Institution runs the National Postal Museum in Washington, DC. When I was home on that side of the country during winter break, my mum and I visited. It was surprisingly fun!
I sent myself a postcard from their stamp shop/post office:
And of course I used one of the Postal Museum stamps issued way back when the postage for a letter was only 29 cents. Now that much won’t even cover the cost to mail a postcard! But I love that I got this interesting cancellation on this stamp.
The postcard shows Owney the railway mail dog, who is the unofficial mascot for the Railway Mail Service. Now, the Railway Mail Service doesn’t exist anymore, but back in the late 1800s it was still operating and Owney rode the trains with the mailbags, eventually traveling all the way around the world. Owney certainly outlasted the Railway Mail, not only in the charming story, but also because his actual stuffed and preserved body is on display in the museum. That’s a little weird to me.
Finally, they were giving away postcards at their newest exhibit, Systems at Work, which chronicles the history of mail delivery systems. If anyone wants to trade for one of these, I have a ton: