1846

1846 was a year marked by warfare, territorial change, and scientific breakthroughs. In North America, the Mexican–American War escalated after the United States annexed Texas; fighting began on April 25, 1846, with the Battle of Palo Alto, and the U.S. Congress declared war on Mexico in May. The conflict would reshape the map of North America and culminate in the 1848 Treaty of Guadalupe Hidalgo, which transferred large areas to U.S. control.

In California, a brief Bear Flag Revolt proclaimed the California Republic on June 14, 1846, before U.S. forces secured the region during the war and integrated it into the United States. In the Pacific Northwest, the Oregon Treaty, signed on June 15, 1846, settled the U.S.–British boundary along the 49th parallel to the Pacific, with Vancouver Island remaining British.

In science, Urbain Le Verrier’s calculations led to the discovery of Neptune; observation of the planet was confirmed on September 23, 1846 by Johann Galle, marking a major achievement in astronomy.

In institutional history, the Smithsonian Institution was established in 1846 when Congress accepted James Smithson’s endowment, creating a center for research and public education.

These developments underscored a year of expansion, conflict, and inquiry, laying groundwork for subsequent American territorial growth, scientific discovery, and the establishment of enduring public institutions.