The citizen soldier has long been an important part of American military history. During the Revolutionary War, the ideal of the citizen soldier stood in opposition to the Hessian mercenaries and British standing army, which harassed the American colonists. An important part of the ethos of the burgeoning American democracy, the citizen soldier represented the will of the people. Today, the idea is best exemplified by the National Guard, volunteers serving to defend the nation without becoming full-time professional soldiers.

Chicago's Pritzker Military Library is a unique collection focusing on "the concept of the citizen soldier as an essential element for the preservation of democracy." Opened in 2003, the library offers over 25,000 volumes on the citizen soldier, mainly from the 20th century, as well as original military posters, recruitment art, magazine and soldiers' journals. Swords and other memorabilia from the Civil War, including glass negatives, are held in the collection. The library also boasts many artifacts related to the British statesman Winston Churchill.

In 2009, the library received the National Medal for Museum and Library Science. It is the only library of military history that is free and open to the public.