What are Primary and Secondary Sources?

Contents of President Abraham Lincoln's pockets on the night of his assassination. 

Contents of Abraham Lincoln's Pockets on the Night of His Assassination on Exhibit at the Abraham Lincoln Bicentennial Exhibit. Library of Congress           Thomas Jefferson Building, Washington, D.C. Digital image. Library of Congress. N.p., n.d. Web. 1 Dec. 2015.

A few years ago I took an excellent online class which was all about the Library of Congress and utilizing its primary sources. It was amazing to see how many resources had been digitized, (they are not done quite yet with all the items) and how they could be used in the classroom. 
Ask your students if they can explain the difference between primary and secondary resources, and you will probably find that they do not know the answer. 

A primary resource is the original document, including photos, newspapers, birth certificates

Secondary sources evaluate or discuss primary sources.

Here's a short video explaining primary and secondary resources:

This table shows you the differences side-by-side:

Here are some digital photographs and primary sources from the Library of Congress'
Civil War Glass Negatives and Related Prints Collection: 

Officers of General Grant's Staff,City
Point, Va. 

March 1865

Federal dead on the field of battle the first day Gettysburg, PA