Harvard University’s Immigration to the United States, 1789-1930, which is available through their Open Collections Program, is a great resource that offers interesting primary sources that one cannot easily find elsewhere. This collection offers a wide range of material, including photographs, manuscripts, and books and pamphlets. While the focus is on immigration between 1789 and 1930, there is plenty of information on issues related to the Civil War era. One can browse the collection by theme (including “Immigration, Railroads, and the West” and “Gold Rush”) and topic (including Attitudes Towards Immigrants, Living Conditions, Reasons for Immigration, Working Conditions). Also check out their map collection and links to other digital resources on this subject.