The original Declaration of Independence can be found in the rotunda of the National Archives Building in Washington, D.C. The Rotunda for the Charters of Freedom is the permanent home for the Declaration of Independence, Bill of Rights, and the U.S. Constitution.
The Public Vaults exhibit is a permanent display of the archival treasures relating to United States history. Presidential letters, wartime documents, photographs are included throughout the Vaults exhibit. Visitors can learn quite a bit about the history of the country.
Everyone can come and explore the great issues and documents of American history for free.
If you do not get the opportunity to visit in person, you should go to the Digital Vaults website and explore the 1200+ historical documents archived there. You might also be interested in researching the specific National Archives website for more valuable information.
The reference format for the Declaration of Independence depends on how you accessed the document. If you worked from a copy found within a book or e-book, you would use a book reference type. If the document was found on the web, you would cite the document as an article on website.
A few examples are below:
Lossing, B. J. (1997). The Declaration of Independence with short biographies of its signers.
Carlisle, MA: Applewood Books.
The Declaration of Independence. (n.d.). Retrieved from http://www.archives.gov/exhibits
Declaration of Independence [Kindle version]. (n.d.). Retrieved from www.amazon.com