On this day in History - April 6

1453 – Mehmed II begins his siege of Constantinople. The city falls on May 29 and is renamed Istanbul.

1808 – John Jacob Astor incorporates the American Fur Company, that would eventually make him America's first millionaire.

1830 – Church of Christ, the original church of the Latter Day Saint movement, is organized by Joseph Smith and others at either Fayette or Manchester, New York.

1965 – Launch of Early Bird, the first commercial communications satellite to be placed in geosynchronous orbit.