Harris spent many years researching the topic "the first peopling of America." Most of the materials in this collection are his research notes, including extracts from printed sources. There is information on the natural history of North and South America, and an eclectic assortment of notes on American Indians, ancient Chinese and Japanese inscriptions, biographies of early American ministers, epitaphs, genealogies, and archaeology. Harris was also interested in the church history of Massachusetts and he recorded much information on influential Colonial clergymen. He did not complete a book on the original peopling of the Americas, but the octavo volume in this collection appears to be a fairly thorough manuscript copy of what he may have intended to publish. It is titled "Researches into the origin of the Indigines [sic] of North and South America, and the Sources of their primitive history; with illustrations of their antiquities." Throughout this volume and the rest of the collection there are drawings of pottery, implements, and early fortifications. The collection also includes one small volume of sermon notes, 1793-1801, and one folder of correspondence, 1809-1842. The letters concern his historical research, church business, and the American Antiquarian Society, which he served as Corresponding Secretary.
