I agree! I'd like to liven things up by saying that the very first letterbox planted in the U.S. was the Prayer Rock box, but I'm sure that won't generate any discussions.

Snopes: WRONG!

Correct Answer:

The United States Post Office Department began installing public letterboxes in the 1850s outside post offices and on street corners in large Eastern cities. U.S. letterboxes were initially designed to be hung or supported, and were mounted on support pillars, lamp-posts, telegraph poles, or even the sides of buildings. By the 1880s, these letterboxes were made of heavy cast iron to deter theft or vandalism. As letterbox volume grew, they were replaced with other free-standing models. After the late as the 1960s, most letterboxes were replaced with a rigid plastic variety that could be more easily placed in any desired location, such as "Prayer Rock". The rest is history.