Series I consists chiefly of correspondence between Kingman Brewster and Mary Louise Phillips Brewster from 1941 (post-Yale graduation) to 1944, and correspondence to and from one or both of them covering 1946 to 1960 and 1977 to 1984. The most substantive correspondence is written by Kingman between 1941 and 1960. This correspondence documents his thoughts about his career, the development of his political philosophy, and early connections with persons, including Roger Baldwin, McGeorge Bundy, Ray Garrett Jr, and L. Douglas Heck, who later became significant figures in politics, law, and business. It also provides information about his tenure with the Economic Cooperation Administration. The 1977 to 1984 correspondence is mostly incoming and social in nature.