Rows upon rows of “virtual stacks” now stretch as far as the eye can see. From JSTOR to the Library of Congress to Ancestry.com, unprecedented quantities of historical material are being added to the digital ether. In fact, you are probably reading these words on a screen right now. Search-box interfaces allow historians to instantly query vast quantities of historical material in order to pull out information about individuals, events, institutions, and locations. With just a few strokes of a keyboard, a historian can sift through millions of digitized pages of newspapers, government documents, or books. A process that would have once taken a lifetime of flipping through microfilm or archival folders can be conducted in just a few minutes. As historian Lara Putnam notes, this now “feels as revolutionary as oatmeal.” But, she argues, the “mass digitized turn” has nevertheless had a profound impact on the practice of history in ways that the discipline is only beginning to understand. This is especially true for a field like modern American history, where an abundance of easily scannable English-language sources has generated a wealth of online material.