French mathematician Urbain Le Verrier submitted refined orbital calculations for a predicted eighth planet, work that would guide telescopes to Neptune within months.

US Navy forces under Commodore John Sloat raised the American flag over Monterey, California, claiming the territory during the Mexican-American War.

President James Polk signed the act establishing the Smithsonian Institution, built on a British scientist's bequest to a nation he never visited.

Astronomer Johann Galle located Neptune within an hour of resuming his search, guided by predictions from Urbain Le Verrier's mathematics.

Berlin astronomer Johann Galle spotted Neptune within a degree of its predicted position, confirming a planet found first by mathematics, not a telescope.