The American Historical Association has put together this page on finding and evaluating archival resources that can be a good start for your search: Finding and Evaluating Archives
This source contains letters, journals, images, and more that cover all aspects of the migration experience, from motives and departures (from Europe and Asia) to arrival and permanent settlement (in North and South America as well as Oceania).
Dates: 1800-1924 CE
A primary source archive of images, writings, economic accounts books, maps, and more about the trading and cultural relationships between China, America and the Pacific region, with a heavy focus on the 19th Century.
Dates: 1648-1997 CE
Full-text historical news articles in major American and British newspapers, including the New York Times, Boston Globe, Chicago Tribune, Washington Post and more.
Dates: 1791-2003 CE
Full text of more than 1,000 historical U.S. newspapers. Contains Early American Newspapers, 1690-1922, and African American Newspapers, 1827-1998.
Dates: 1690-1998 CE