1. There is still one route left in the country where mail travels by mule.
2. There's a special postmark for Supai's outgoing mail, so you'll know your mail was carried by mules.
3. The Post Office Department was founded in 1775 by the motherflipping Founding Fathers themselves. It is the second oldest federal department in the U.S.
4. Benjamin Franklin was fired from his postmaster general gig by the British Crown in 1774. He was reappointed postmaster general by himself and other Continental Congress members in 1775.
5. George Washington was on the first general-issue stamps released in 1847; he's been on more stamps than any other person.
6. Before he became president, Abraham Lincoln was a postmaster.
7. Although mail was delivered directly to individual houses starting in 1863, mailboxes or slots weren't required everywhere until 1923.
8. The first commemorative stamp was issued in 1893 to honor a white guy — a (white) woman* had her own commerorative stamp in 1902. USPS didn't issue a stamp honoring an African American until 1940: Booker T. Washington.
9. In the 1930s, mail went by sailboat between Kelley's Island and Sandusky, Ohio, 10 miles away. In bad weather, the boat went straight from the island to the nearest mainland port, a four-mile trip which could take 8 hours in bad weather.
10. Zoning similar to ZIP codes was only established after thousands of postal workers left for military service during WWII.
11. The Chicago Post Office shut down for a week in 1966 because, as one postmaster put it, "We had mail coming out of our ears."
12. You know that phrase "Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds"? That's not really the USPS motto. The Postal Service has no motto.
13. The Postal Service has an unofficial mascot: Owney the well-traveled terrier.
14. Owney was put down in 1897 after he bit someone. He was stuffed and is now on display in the National Postal Museum.
15. This has been the postal seal since 1970, but before that it was a man on a horse. And before that it was the pagan god Mercury.
16. The Postal Service sorts and delivers more than 700 million pieces of mail each day. Except Sunday.
17. Mail took so long to travel west in the mid-19th century that Los Angeles didn't find out California had become a state of the Union until six weeks after the fact.
18. The Pony Express was in operation for less than two years. Its actual name was the Overland Express Route.
19. The name of the post office in Joliet, Ill., was Juliet, and then Romeo, and then Juliet again, and then Joliet.
20. There has never been a woman postmaster general.
Information from USPS' The United States Postal Service: An American History.