1858
Albert Potts patents the first street-mounted mailbox in the United States on March 9, 1858, greatly improving urban postal systems and making public mail deposit more convenient in growing cities.
1893
On March 9, 1893, James Dewar reports freezing air into a transparent solid, advancing cryogenic science and the study of extremely low temperatures in laboratory conditions.
1900
Howard H. Aiken is born on March 9, 1900. He later developed the Harvard Mark I, one of the earliest electromechanical computers, helping accelerate large-scale scientific calculation.