Snail mail doesn’t sound thrilling, but the United States Postal Service is anything but boring. USPS workers serve some of the most far-flung places in the country and process more than 400 million pieces of mail each day—including hundreds of thousands of letters to Santa each year. Here are a few facts about the letter carriers in your life.

1. The United States Postal Service was created via a constitutional amendment.

Benjamin Franklin was appointed the first Postmaster General in 1775. When the U.S. Constitution was ratified in 1789, Article I, Section 8, Clause 7 gave Congress the ability to “establish post offices and post roads.” In 1792, President George Washington signed the Postal Service Act, creating the Post Office Department. Nearly two centuries later, the United States Postal Service as we know it was created. Today, the USPS employs more than 7.3 million people.

2. Some United States Postal Service mail is delivered by mule.

Trusty mail carriers hoofing it down the Grand Canyon.Elf, Wikimedia Commons // CC BY-SA 3.0

How do you get mail to the bottom of the Grand Canyon? By enlisting the help of mules. Every day, mule trains deliver about 4000 pounds of mail, food, supplies, and furniture to the village of Supai. The local Havasupai tribe receives its mail after an 8-mile journey by 50 horses and mules. Since so much of the mail is perishable, the post office where this route originates in Peach Springs, Arizona, has walk-in freezers.

3. The USPS also uses postal boats.

Meanwhile, in Michigan, a 45-foot mail boat, the J.W. Westcott II, has a contract to deliver mail to passing ships sailing on the Detroit River. Legally, the postal service has to deliver mail to all Americans, even those aboard ships. The mail boat pulls alongside larger vessels, which lower down a bucket on a rope that can be filled with correspondence—the custom is known as “mail in the pail.” The boat even has its own special ZIP code: 48222.

The Detroit River isn’t the only place where you can receive your mail by boat. In Alabama’s Magnolia River, 176 homes on the 31-mile route receive their deliveries from a 15-foot boat that pulls right up to fixed mailboxes on their docks.

4. The longest United States Postal Service mail route is more than 190 miles.

Sidney, Montana, boasts an unusual claim to fame: The remote town has the longest rural delivery mail route. The mail carrier travels a whopping 190.7 miles.

5. The shortest USPS rural mail route is under 3 miles.

Not every carrier is piling up the daily mileage. The mail carrier in Parker, Colorado, has it relatively easy, only traveling 2.3 miles each day. The USPS says its shortest rural delivery route is Carrollton, Texas, a job that requires just 1.2 miles of daily travel.

6. The United States Postal Service has its own stamp cave.

Some of the most valuable stamps in the country are housed within SubTropolis.Americasroof, Wikimedia Commons // CC BY-SA 3.0

Need a stamp? Try looking in SubTropolis, a sprawling excavated limestone mine in Kansas City. Many companies operate out of the underground industrial park, and the USPS has gotten in on the act. The temperature and humidity level 150 feet underground make it an ideal hub for stamp storage and distribution.

7. The USPS also has a facility to decipher terrible handwriting.

Ever wonder how the USPS decodes awful penmanship? It calls in the experts. The Remote Encoding Center in Salt Lake City receives the system’s impossible-to-read mail. The center’s 1000 workers there take on every piece of mail that’s too challenging for the automated mail sorters to decipher or is otherwise incorrectly addressed. According a 2013 Deseret News report, these workers can translate a scribbled envelope into legible, usable delivery information in an average of four seconds.

8. United States Postal Service mailboxes weren’t always blue.

The postal service began painting its street mailboxes blue in 1971 [PDF], when it made the structural switch from the Post Office Department to the United States Postal Service. The color of boxes had varied in the century before that, including a stint in drab olive green after World War I thanks to a surplus of paint in that color.

9. The current postmaster general of the USPS started as a letter carrier.

In February 2015, Megan J. Brennan became the first female postmaster general in the United States. She rose up through the postal ranks, starting with a job as a letter carrier in 1986.

10. Dog attacks actually happen to workers for the United States Postal Service.

Postal workers, beware.Stebunik, Wikimedia Commons // CC BY 3.0

Dogs actually do attack USPS workers. In 2014, dogs attacked 5767 postal employees. Los Angeles was the biggest hotbed of canine attacks, with 74 mail carriers incurring pets’ wrath. Mail carriers are instructed to keep their satchels between their bodies and an aggressive dog, using the sack of mail as a buffer.

Dogs aren’t the only animals mail carriers have to worry about: Wasps have been known to build nests inside mailboxes.

11. The United States Postal Service helps crack criminal cases.

The USPS is skilled at catching criminals in the act. In 2013, law enforcement seized 46,000 pounds of narcotics from the mail and identified 778 criminals from fingerprints and other physical evidence found in mail.

12. Famous figures like Walt Disney and Steve Carell had mail service jobs.

Before they became household names, some political, literary, and TV greats had postal jobs. A 16-year-old Walt Disney was a mail carrier in 1918. William Faulkner served as the University of Mississippi’s postmaster from 1922 to 1924—he hated the job, and resigned after a postal inspector was sent to investigate complaints filed against him. In more recent history, comedic actor Steve Carell worked a rural mail route in Massachusetts.