A project of the Library of Congress called "Primary Documents in American History" is just one more example of this type of site. Although there will be future updates, at this writing this site offers us the ability to see original documents (in digitized form) of documents that take us back to watershed (or less earth-shaking) events in our history.
To quote the introduction of the site itself:
The Library of Congress is home to many of the most important documents in American history. This Web site provides links to materials digitized from the collections of the Library of Congress that supplement and enhance the study of these crucial documents.
The links at right highlight eras of American History. Each of these sections link to a list of important documents from that era. For each item...... there is a page with background information about the document, a list of links to digital materials concerning that document from the Library's site and elsewhere, and bibliographies both for general readers and for younger readers.
The initial release of this Web site contains documents from the years 1763 to 1877. Updates will be made on a regular basis, including the addition of documents from the 20th Century.
I spent some time reading the original Emancipation Declaration. It's impossible not to feel that sense of history in the making, even these many years afterward.
As a sample, you can also view the Declaration of Independence, the Constitution, the Louisiana Purchase, Jefferson's Secret Message Regarding the Lewis and Clark Expedition, the Gettysburg Address, and many more.
