American Board of Commissioners for Foreign Missions
The American Board of Commissioners for Foreign Missions (ABCFM), founded in 1810, was the first organized missionary society in the United States. During its 150-year history, the Board was responsible for over 100 mission stations around the world, from which missionaries sent voluminous letters with an immense amount of information--social, political, and geographic, as well as religious--about the regions in which they operated.
The ABCFM Archives are in the Houghton Library (see the Finding Aid, a list of the documents contained in the archive). Many of them have been microfilmed, but only a small portion has been digitized. (See the "Digital Material" tab in the Finding Aid.) In the list of the microfilm reels, the documents relating to the "Near East" start at the bottom of page 41.
To find other archives at Harvard that have material about the Middle East, go to HOLLIS Archives and search by keyword, e.g. Syria. To see archives that have been digitized, select the Limit for digital materials.