The following are links to 18th, 19th, and 20th century Church History documents available online, in English, for free. In some cases, there are better translations or editions available in print, so for serious scholarly publications, you will want to consult those. But for introductory purposes, the following links may be helpful.
• Books by Baptist authors (Galusha Anderson, Thomas Armitage, Joshua Bradley, Isaac Burgess, Ernest DeWitt Burton, Shirley Jackson Case, William Newton Clarke, John Marvin Dean, John Dowling, Charles W. Eliot, Daniel Faunce, Harry Emerson Fosdick, George Burman Foster, James R. Graves, R. H. Graves, William R. Harper, Hezekiah Harvey, Alvah H. Hovey, Eri B. Hulbert, Henry Mabie, Robert S. MacArthur, G.W. McPherson, Shailer Mathews, Ernest Pickering, Walter Rauschenbush, T. D. Teasdale, Chester Tulga, Henry Clay Vedder, William R. Williams) - (baptiststudiesonline.com)