PBS
Lewis and Clark: Archives: A Timeline of the Trip
An easy-to-follow timeline of Lewis and Clark and their journey to the West beginning with Jefferson's ideas of an expedition in 1806 to the death of William Clark in 1838.
Library of Congress
Loc: Declaring Independence: Drafting the Documents
This page from the Library of Congress links directly to a chronology of events leading to the declaration of independence from Great Britain, the drafting of the document, and Jefferson's vison as stated in the Declaration of Independence.
Library of Congress
Loc: America's Story: Louisiana Purchase
This Library of Congress timeline series discusses the Louisiana Purchase.