August 4 – The 2nd United States Census is conducted. It finds 5,308,483 people living in the U.S. of which 893,602 are slaves.
August 30 – Gabriel Prosser's slave revolt in Richmond, Virginia is postponed due to weather. Word of his plan reaches Virginia's governor, James Monroe, who calls in the state militia. Gabriel is later captured and hanged on October 10 along with 23 other slaves.
September 30 – The Convention of 1800, or Treaty of Mortefontaine, is signed between France and the United States of America, ending the Quasi-War.