Letters written to Gay from political and literary contemporaries such as Horace Greeley, Charles Sumner, and William Bryant; reports in letter form from his reporters at the front during the Civil War; and personal correspondence including many letters from his wife, Elizabeth Neall Gay. Letters written to Mrs. Gay from family friends and business associates including many from her husband. Correspondence of other members of the Gay family including Walter Gay, Sarah Gay, and Allan Gay. Diaries, notebooks, and journals of Sydney Howard Gay.

The Willard L. Severinghaus Papers include the personal and professional papers of Columbia University Physics professor Willard Lesly Severinghaus, as well as a small amount of material related to the extended Severinghaus family. There are also record books from the Terre Haute, Indiana German Methodist Episcopal Church where Severinghaus's father, John F. Severinghaus, was pastor.

The records of W.R. Grace & Co. cover the rise of the Grace shipping business from 1864 until World War II. The early correspondence concerns all aspects of the shipping business in New York and South America, mining interests in Peru and Chile, the railroad in Costa Rica, the inter-ocean canal planned for Nicaragua, and political interests throughout Central and South America. There are letter books, correspondence, and scrapbooks of clippings for all aspects of W.R. Grace's career. There are minute books and other documents for more than 50 subsidiary companies owned by W.R. Grace & Co. or by family members. The papers of Joseph Peter Grace (1872-1950) continue the business, family, and philanthropic activities until 1942. There are also 20 reels of motion picture film about the Grace Co. South American interests in the 1950s.