ICONS: Lewis & Clark, Louisiana Purchase, Robert Fulton's Steamboat
- John Chapman (a.k.a. Johnny Appleseed) begins handing out apple seeds and seedlings to Ohio settlers in 1800.
- The U.S. Library of Congress is founded on April 24, 1800.
- The United States and North African Berber Muslims fight the First Barbary War from 1801 to 1805 in an effort to halt Barbary pirates' attacks upon American merchant shipping.
- The "District of Columbia Organic Act of 1801" creates the planned city and capital of the United States under the jurisdiction of the U.S. Congress.
- The first edition of the New York Post is published November 16, 1801.
- Martha Washington, America's first "First Lady" dies May 22, 1802, at Mount Vernon, VA.
- Lewis and Clark begin their expedition to map the northwest United States on May 14, 1804.
- Alexander Hamilton dies following a duel with Vice President Aaron Burr on July 11, 1804.
- Painter Charles Willson Peale establishes the Pennsylvania Academy of the Fine Arts in 1805.
- Noah Webster publishes his Compendious Dictionary of the English Language in 1806.
- President Thomas Jefferson signs "The Act Prohibiting Importation of Slaves of 1807" into law on March 3, 1807, ending the transatlantic slave trade.
- On April 11, 1803, while negotiating to purchase New Orleans, LA, from the French for $10 million, the U.S. delegation headed by Robert R. Livingston is dumbfounded to be offered the 828,800 square mile "Louisiana Purchase" instead for $15 million. Livingston accepts without consulting President Thomas Jefferson to prevent Napoleon from rescinding the offer.
- On February 11, 1809, Robert Fulton patents his steamboat and soon after begins offering services on major rivers and the Chesapeake Bay.
- Future 16th President of the United States Abraham Lincoln is born on February 12, 1809, in Hardin County, KY.