Georgetown University has made available several documents pertaining to Charles Guiteau, the man who assassinated President James Garfield. Correspondence to and from Guiteau, and other printed material about Guiteau, are included in the collection.
Several speeches and essays by Theodore Roosevelt, including "The Strenuous Life," are available at this site.
AMDOCS: Documents for the Study of American History provides links to historical documents available online. Dozens of documents from the Gilded Age are included in this chronologically arranged catalogue.