• American Memory - Library of Congress
  "American Memory is a gateway to rich primary source materials relating to the history and culture of the United States. The site offers more than 7 million digital items from more than 100 historical collections."
• Archiving Early America
  "Here at Archiving Early America, you will discover a wealth of resources -- a unique array of primary source material from 18th Century America. Scenes and portraits from original newspapers, maps and writings come to life on your screen just as they appeared to this country's forebears more than two centuries ago."
• Documenting the American South
  "Documenting the American South (DAS) is a collection of sources on Southern history, literature and culture from the colonial period through the first decades of the 20^th century." 
• Making of America
  "Making of America (MoA) is a digital library of primary sources in American social history from the antebellum period through reconstruction. The collection is particularly strong in the subject areas of education, psychology, American history, sociology, religion, and science and technology. The collection currently contains approximately 8,500 books and 50,000 journal articles with 19th century imprints."
• National Archives and Records Administration
  "The Archival Research Catalog (ARC) is the online catalog of NARA's nationwide holdings in the Washington, DC area, Regional Archives and Presidential Libraries." 
• 19th Century Documents - Furman University
  "When completed this collection will include accurate transcriptions of many important and representative primary texts from nineteenth century American history, with special emphasis on those sources that shed light on sectional conflict and transformations in regional identity. Because of our location in South Carolina and the salient role of its natives in the era's history there will also be a number of materials relevant to South Carolina or South Carolinians." 
• Emergence of Advertising in America - 1850 to 1920
  "The Emergence of Advertising in America: 1850 - 1920 (EAA) presents over 9,000 images, with database information, relating to the early history of advertising in the United States. The materials, drawn from the Rare Book, Manuscript, and Special Collections Library at Duke University, provide a significant and informative perspective on the early evolution of this most ubiquitous feature of modern American business and culture."
• Ad Access - 1911 to 1955
  "The Ad*Access Project, funded by the Duke Endowment "Library 2000" Fund, presents images and database information for over 7,000 advertisements printed in U.S. and Canadian newspapers and magazines between 1911 and 1955."
• Historic American Sheet Music
  "The Rare Book, Manuscript, and Special Collections Library at Duke University holds a significant collection of 19th and early 20th century American sheet music. The Historic American Sheet Music Project provides access to digital images of 3042 pieces from the collection, published in the United States between 1850 and 1920."
• US Historical Documents: University of Oklahoma College of Law
  A chronology of US historical documents - coverage is Pre-Colonial Era to Present 
• Documents for the Study of US History
  Arranged by date, coverage is years 1400 to Present

(updated 11/3/2015)