Long-time associate of Richard Neutra, Thaddeus Longstreth was born in Cincinnati, OH, later earning a graduate degree in Architecture in 1938 and an MFA in 1941 from Princeton's Graduate School of Architecture. After serving in the Navy, Longstreth entered the office of Richard Neutra as a draftsman in 1946working on several important projects. He moved to Philadelphia in 1947, working in different architecture offices on several important projects including the Greater Philadelphia City Planning exhibit and a number of Philadelphia Redevelopment Authority projects. Longstreth opened his own office in Washington Crossing, Pennsylvania in 1950. Beginning in 1953, he collaborated with Neutra on a number of houses in the region, and was the East Coast resident supervising architect for Neutra & Alexander on several projects, including the Lincoln Memorial Cyclorama and Visitors' Center for the National Park Service at Gettysburg, Pennsylvania.
This collection is the primary archive of the architectural work of Thaddeus Longstreth. The bulk of the collection comprises records of Longstreth's architectural practice (111 projects spanning the years 1943 to 1984). The collection also contains a smaller amount of personal material. Longstreth preserved a substantial amount of material related to his collaborations with Richard Neutra, beginning with his work in Neutra's office in California, and concluding with his supervision of Neutra's institutional and domestic commissions in the eastern United States in the 1950s and 1960s.