Charles Adam Platt (1861-1933) was an American architect and landscape designer. Although best remembered today for his landscape and country house designs, he was also nationally known for his etchings, landscape paintings, commercial architecture, and institutional projects. He was largely self-taught in each of these disciplines, building his success on his ability to reconceive the classical tradition in architecture for the needs and desires of his wealthy, powerful clients. This collection contains materials related to Platt's personal and professional lives, the bulk originating from Platt's office in the form of project drawings, photographs, and records documenting architectural projects from 1901-1933.

The collection consists primarily of correspondence. The collection also includes contracts, invoices, inventories, appraisals, specifications, articles, photomechanical drawings and photographs.

Also, a variety of professional and personal miscellany, such as correspondence, clippings, pamphlets, flyers, postcards, invitations, menus, receipts, a diploma, caricatures of colleagues, and Sawyer's monocle

This collection includes original and reprographic architectural drawings, black and white photographic prints, typescript specifications, and other papers relating to the architectural practice of Thomas W. Lamb, as well as his colleague and successor, John J. McNamara.