The United States of America was transformed in the two centuries from the first English settlement at Jamestown in 1607 to the beginning of the 19th century. From a series of isolated colonial settlements hugging the Atlantic Coast, the United States evolved into a new nation, born in revolution, and guided by a Constitution embodying the principles of democratic self-government.

The United States transformed itself again in the 19th and early 20th centuries. A rural, agricultural nation became an industrial power whose backbone was steel and coal, railroads, and steam power. A young country once bound by the Mississippi River expanded across the North American continent, and on to overseas territories. A nation divided by the issue of slavery and tested by the trauma of civil war became a world power whose global influence was first felt in World War I.

The monuments of American history span a continent in distance and centuries in time. They range from a massive serpent-shaped mound created by a long-gone Native-American culture to memorials in contemporary Washington, D.C., and New York City.

For the United States, the 20th century was a period of extraordinary turmoil and change. In these decades, the nation endured the worst economic depression in its history; emerged triumphant, with the Allies, in World War II; assumed a role of global leadership in the century's twilight conflict known as the Cold War; and underwent a remarkable social, economic, and political transition at home. Where once the United States transformed itself over the slow march of centuries, it now seemed to reinvent itself almost by decades.

The first years of the new century unleashed a new threat to peace and democracy: international terrorist attacks that killed and maimed thousands in the United States and around the world. Just as it has with earlier dangers, the United States took up this formidable challenge in unison with its allies. At the same time, it coped with changes sparked by globalization, fast-paced technological developments, and new waves of immigration that have made American society more diverse than in the past. The country sought to build upon the achievements of its history, and to honor those who have sacrificed in its cause.

• Historians on America - Eleven historians look at developments and ideas that changed America
• Outline of U.S. History
• 100 Milestone Documents - NARA: A list of 100 milestone documents, 1776 to 1965
• Avalon Project: Documents in Law, History and Diplomacy -Yale Law School: Key political documents from earliest times to 2001
• The Hypertext Project - Univ. of Virginia:Full texts of books from American history
• Words and Deeds in American History - US Library of Congress, American Memory Project
• America's Story from America's Library Site aimed at children
• American Memory Project Digitized collection from different periods in American history
• Historical Text Archive Articles, books, essays, documents, historical photos, and links
• American History Article Archives American History magazine
• Outline of U.S. History - DOS IIP