For those interested in the social history of the United States I strongly recommend the Open Collections Program of the Harvard University Library, especially the collections "Women Working 1800-1830" and "Immigrations to the United States 1789-1930" (full access and very comfortable):
Women Working, 1800 - 1930 focuses on women's role in the United States economy and provides access to digitized historical, manuscript, and image resources selected from Harvard University's library and museum collections. The collection features approximately 500,000 digitized pages and images including:
* 7,500 pages of manuscripts
* 3,500 books and pamphlets
* 1,200 photographs
Immigration to the United States, 1789-1930, is a web-based collection of selected historical materials from Harvard's libraries, archives, and museums that documents voluntary immigration to the US from the signing of the Constitution to the onset of the Great Depression.
WB.