Mule train delivery

Got mules? The most unusual mode of delivery
used by the Postal Service is the mule train. Since the
1930s, mules have been carrying mail and goods to the
Havasupai people inside the Grand Canyon.

• Daily delivery includes 10-22 mules, along with one
  wrangler on horseback, five days a week, traveling
  nine miles down into the canyon to the Supai
  Post Office.
•  It takes three hours to get down and five hours to
  get up.
• On the way up, the wrangler untethers the mules and
  sends them back on their own.
• Each mule can carry up to 200 pounds, and the
  weight is distributed equally on each side of the
  animal for balance.
• The Supai Post Office has a special Mule
  Train postmark.