Philip B. Downing was the African-American inventor of the public mailbox, a metal box on four legs with an outer door and an inner safety door. He called it a street letter box and intended it to be used instead of the post office.
Downing patented his mailbox on Oct. 27, 1891. Before 1891, safety was not guaranteed in public mailboxes because they were typically left half-open. With Downing's invention, the inner safety door ensured the protection of mail from theft and adverse weather conditions.
In 1890, Downing patented a railway switch controlling the power supply to trains. Residential electrical switches were later invented based on this design.