Although we think of these words as the official motto of the United States Postal Service, they’re not.
The text was inscribed across the front of the James A. Farley Post Office building in New York as a finishing touch in 1912. William Mitchell Kendall, who worked for the architectural firm that designed the building, based the phrase on a quote from Greek historian Herodotus, who wrote about the ancient Persian courier system in the 5th century BC:
“It is said that as many days as there are in the whole journey, so many are the men and horses that stand along the road, each horse and man at the interval of a day’s journey; and these are stayed neither by snow nor rain nor heat nor darkness from accomplishing their appointed course with all speed.”
The USPS actually has no official creed or motto, but that’s OK because I think we all love the unofficial one best.