- Style. In the late 1850s, the first street boxes were attached to public lampposts and walls near busy street corners. As mail volume increased, free-standing package boxes were introduced. These boxes evolved into the standard collection boxes used today.
- Material. The first boxes were made of tin or wood and weren’t very secure. In 1858, locked, cast-iron boxes were adopted. Today’s collection boxes are made of steel.
- Design. Flat-top boxes with an opening for letters on top were used in 1869, followed by a round-top box that opened on the side. In 1889, the opening moved to the front.
- Color. Letter boxes have changed color several times: green, red, white, back to green, red, and green again. Later they were red, white and blue, and changed to the standard dark blue in 1970.
A newly published paper, “Mail Collection Boxes: A Brief History,” has more information:
Source: USPS News Link