Library of Congress

The Library of Congress is a massive online database of several million books, images, recordings, newspapers, art, documents etc. spanning many years and cultures. Considered the "largest library in the world", the Library of Congress is the main research center of the U.S. Congress and the home of the U.S. Copyright Office. (https://www.loc.gov/about/).

Some quick interesting faqs:

• housed in three buildings on Capital Hill
• The LOC began in 1800 inside the capital
• contains over 162 million items!
• in 2015, had over 1.6 million online visitors

The LOC website is very easy to navigate. Starting from the top, you can simply type your search keyword and then click on the magnifying class icon to get your results. 

From there, you can "drill down" your interest in a variety of formats, date, location and other attributes from the left hand sidebar. 

In this case, I chose Photos/Prints/Drawings and then 1800-1899- to find an old image of Harper's Ferry, WV. 

From here, you can download various sizes of the image and under "More Resources", you will find more details about the image such as the title, when it was created (in this case, March 1862), the materials used, notes, where located within the LOC and many other details. 

The LOC is an extremely valuable resource and should definitely be in your research took kit.