Music Premiere
Apr 7 Premiere of Ludwig van Beethoven's "Eroica", in Vienna, conducted by the composer

Ludwig van Beethoven
Historic Expedition
Apr 7 Lewis and Clark Expedition leaves Fort Mandan (on the Missouri River near what is now Washburn, North Dakota), beginning their journey to the Pacific Ocean

William Clark

Sacagawea

Meriwether Lewis
- Apr 27 US Marines attack shores of Tripoli