The United States Postal Service at one time had an unofficial mascot from Albany, New York. He was a mixed bread dog by the name of Owney.
Once a homeless dog that belonged to a mail clerk. Because he loved to sleep on the bags of mail, his owner recommended him for the Railway Mail Service. There he traveled with the mail bags from beginning to end of the rout, he seemed to love the smell of the mail bags.
Owney passed away in 1897 after serving 11 years, and more than 140,000 miles. A taxidermist was able to preserve him and Owney is now on display at the National Postal Museum in Washington, D.C. at the Smithsonian. In 2011 a Postage stamp was introduced with his likeness.
Reference: The Original Dog Bible, Wickipedia