Daniel Urban Kiley (2 September 1912 – 21 February 2004) was an American landscape architect in the modernist style. He designed more than 1,000 projects including the Gateway Arch National Park in St. Louis and the Art Institute of Chicago's South Garden. Kiley was born in Roxbury, Boston, Massachusetts, where his father was a construction manager, grew up in West Roxbury, Boston, and in 1930 graduated from high school in Jamaica Plain. In 1932, he began a four-year apprenticeship with landscape architect Warren Manning, working without pay for the first year, then at 50 cents per hour, during which he learned the fundamentals of office practice and developed an interest in the role of plants in design, sparking his later creative and innovative use of plants in the landscape. From 1936 to 1938, Kiley was a special student in the design program at Harvard University, while continuing work with Manning for 30 hours per week. Among his classmates and friends were Garrett Eckbo and James C. Rose, who also became influential landscape architects. After two years at Harvard, upon Manning's death and the dissolution of his practice, Kiley left without graduating. He worked briefly for the National Park Service in Concord, New Hampshire, and later the United States Housing Authority, where he met architect Louis Kahn. On Kahn's advice, Kiley left the Housing Authority in 1940 to become a licensed practitioner of architecture.