Series I. Correspondence contains business correspondence sent or received by Buck. The correspondence covers a variety of topics, including land sales, the negotiation of leases, scaling methods, and other related topics. The series has been divided into two subseries.

Subseries A. Received contains correspondence received by Buck. The subseries is organized by subject and date. Correspondence received from David Pingree (1841-1932) from 1910-1929 is organized chronologically. Correspondence received in 1934-1935 is organized by subject. Subseries B. Letter Books is comprised of letter books, which contain copies of correspondence sent by Buck. The subseries is organized chronologically, with two books related to the Maine fire patrol and one book related to the log scale commission included at the end of the subseries.