The collection includes over 140,000 pages of correspondence, which serves as a core resource for understanding Wright's personal and professional activities, relationships, and ideas. The correspondence also includes project records such as specifications, contracts, supply orders, invoices and receipts. Letters from the 1880s through the 1920s accounts for only 2% of the total correspondence in the collection (approximately 2,000 documents). The bulk of the correspondence is from the 1930s until Wright's death in 1959.