Union forces under General George McClellan clash with Confederates at the Battle of South Mountain, the first major battle of the General Robert E. Lee's Maryland Campaign.
Winfield Scott captures Mexico City
American soldiers commanded by Winfield Scott enter Mexico City, forcing the Mexican government to enter peace negotiations.
Star-Spangled Banner penned
Francis Scott Key, a Maryland attorney, begins writing the "Defense of Ft. McHenry", later known as the "Star-Spangled Banner." Key had watched the bombing of Fort McHenry from a British ship during a prisoner exchange and awoke to see the American flag flying over the fort.
