Confederate forces attacked Fort Sumter in the harbor at Charleston, South Carolina, officially beginning the American Civil War. Fort Sumter surrendered after thirty-four hours of bombardment.
The Virginia convention voted to secede, making the state the eighth to secede from the Union.
Slave-state Kentucky voted to remain neutral in the conflict.
Tennessee became the last of eleven states to secede from the Union.
The Treaty of Guadalupe Hidalgo ended the Mexican-American War. The US acquired California, Nevada, Utah, New Mexico, and parts of Arizona, Colorado, Kansas, and Wyoming.
Democratic Congressman David Wilmot submitted an amendment to a military appropriations bill prohibiting slavery in any territory acquired from Mexico. The proviso passed the House twice but was defeated in the Senate.
South Carolina’s legislature became the first to approve a convention to consider secession. It also determined to raise 10,000 men for the defense of the state.
Although it was a slave state, Delaware voted to stay in the Union.
Pro-slavery forces won the territorial elections in Kansas. Anti-slavery forces responded by setting up an opposing government in Topeka.
Louisiana seceded from the Union, the sixth state to do so.