This decade was a period of exploration. The most famous explorers were Meriwether Lewis and William Clark who led the expedition into the west during 1804-1806.

1800:
The U.S. Capitol is moved from Philadelphia, and Congress convenes in Washington D.C. for the first time. By secret treaty, Spain cedes the Louisiana Territory to France. Second census: U.S. Population- 5,309,000.

1801:
Thomas Jefferson is inaugurated as the third President of the United States in the first Presidential inauguration to be held in Washington, D.C. Johnny Appleseed (real name John Chapman) arrives at Licking County, Ohio with a bag of apple seeds.

1802:
The "right of deposit" for Americans is withdrawn by the Spanish in New Orleans. American pioneers west of the Appalachians are greatly alarmed by this move, since New Orleans is the only port through which they can sell their products profitably. The move prompts President Jefferson to begin negotiations for the purchase of New Orleans, which culminate in the Louisiana Purchase.

1803:
France sells Louisiana to the United States for $15,000,000. This first territorial expansion of the U.S. west of the Mississippi totals 828,000 square miles. Army officers Meriwether Lewis and William Clark are chosen by President Jefferson to lead an expedition from St. Louis to the Pacific Ocean, for the purpose of discovering a direct water route across the continent and to keep records of the natural resources of the new land, with the aim of establishing an American presence in the northwest through trade and settlement.

1804:
The expedition of Meriwether Lewis and William Clark sets out from Camp Wood, Illinois, near St. Louis, Missouri, on May 14.

1805:
Meriwether Lewis and William Clark reach the Pacific Ocean on November 18, 1805.

1806:
Meriwether Lewis and William Clark return to St. Louis, Missouri on September 23; their expedition has established an overland route to the Pacific Ocean.

1807:
Reports by Lewis and Clark of the richness of beaver and otter in the trans-Mississippi west lead to the formation of the Rocky Mountain fur trade by American trappers and traders.

Congress passes an act prohibiting the African slave trade and the importation of slaves into any place within the jurisdiction of the United States after January 1, 1808.

1809:
James Madison is inaugurated as the fourth President of the United States. The first successful sea voyage by steamboat is made by John Stevens' Phoenix, which sails from New York City to Philadelphia. Meriwether Lewis dies while traveling to Washington, D.C., on the Natchez Trace. A dispute arises as to whether he was murdered or committed suicide. The Missouri Fur Company is chartered by the Chouteau family.

1810:
Third census: U. S. population- 7,239,000.

1810-1820>