One of the most influential upon Kiley was the gardens of the Palace of Versailles. The symmetry and control that its designer, André Le Nôtre, created in the gardens inspired much of Kiley's subsequent work.
After the war, Kiley returned to the United States to open his own office. He tried a few different locations before settling in Charlotte, Vermont. Kiley lived on a 350-acre farm with his wife, Anne, and their eight children. The family entertained often and enjoyed the rural life replete with swimming, boating, and camping. Douglas Martin reported in the New York Times that Kiley once stated that he was inspired by the land around him and that he did his best work there because it made him happy.
This post-war era was the beginning of a long period of productivity and work for Kiley. He teamed with architect Eero Saarinen several times on major projects. In 1947 they worked on the Jefferson National Expansion Memorial in St. Louis-which led to the St. Louis Arch. Unfortunately, Kiley was removed from the team before the project finished and his landscape designs were not implemented. In 1955 he and Saarinen designed the Miller house and grounds. In 1963, they collaborated on the designs for Dulles Airport in Washington, D.C. His later designs included gardens for the Air Force Academy in Colorado Springs, Colorado, and the Oakland Museum in California.
Kiley never formally taught nor did he write treatises on his philosophy of design. Instead he focused on his personal designs while also mentoring inexperienced landscape architects. He was called upon by President John Kennedy to serve on his advisory council. In later years his contributions and talent were well recognized and awarded. In 1997, President Clinton awarded him the National Medal of Arts. In 2002, he was given the National Design Award for lifetime achievement by the Smithsonian's Cooper-Hewitt National Design Museum. Also in 2002, he was made an honorary Fellow of the Royal Institute of British Architects.
Kiley died on February 21, 2004, after a period of illness; he was 91. Kiley is survived by Anne, his wife of 61 years; his eight children, 19 grandchildren, and one great-grandson. His designs were a major contribution to and influence on 20th century landscape architecture. Kris Jarantoski, director of the Chicago Botanic Garden told Blair Kamin of the Chicago Tribune, "He had a fresh perspective for Americans on landscape architecture . He reorganized nature."