The papers of Frederick Law Olmsted (1822-1903) span the years 1777 to 1952, with the bulk of the material dated 1838 to 1903. The papers document Olmsted's varied careers as farmer, journalist, editor, and landscape architect, as well as his private life. The collection consists of journals, correspondence, letterbooks, business papers, legal and financial papers, maps, drawings, reports, speeches, lectures, essays, articles, book manuscripts, scrapbooks, newspaper clippings, and miscellaneous items. Numerous family papers are also included.

Journals in the collection were kept from 1777 to 1888 by various members of the Olmsted family. The earliest is by Gideon Olmsted (1749-1845) describing his adventures as a privateer, with additional papers concerning his thirty-year suit against the Commonwealth of Pennsylvania claiming prize money for a vessel he captured in the Revolutionary War. There are six journals of John Olmsted, father of Frederick Law Olmsted, which record not only the activities of the Olmsted family, such as trips, expenses, illnesses, and births and deaths, but also local and national events. These journals begin in 1825 and continue with several gaps to 1888. The later entries were made by Mrs. Mary Cleveland Perkins Olmsted after the death of her husband in 1873. There is little material by Frederick Law Olmsted in this series with the exception of two journals covering brief periods in 1843 and 1863.

The Correspondence series contains both personal and business letters. A large number of family letters, particularly from Olmsted's father, John, and brother, John Hull, dominate the early years while correspondence with his son, Frederick Law Olmsted, Jr., and nephew and stepson, John Charles Olmsted, is found with increasing frequency in later years. Business details in these letters relate to John Olmsted's support for his son's early ventures in farming and publishing and Frederick Law Olmsted's son and stepson, who exhibited considerable ability as landscape architects and eventually assumed positions in the family firm.

Correspondence with friends and business associates relates to almost every phase of Frederick Law Olmsted's professional career, from his commission in 1852 by the editor of the , Henry J. Raymond, to investigate slavery in the South, to his last creative efforts shortly before his retirement in 1895 in the landscape design of Biltmore, the North Carolina estate of George W. Vanderbilt. The papers include material on his brief partnership with the publishers of his long association with New York's Central Park, his two years as manager of John C. Frémont's Mariposa mining estates in California, and his career in city and regional planning.

For the Civil War period, there are papers documenting Olmsted's work as general secretary of the United States Sanitary Commission and his activities relating to former slaves. Other papers related to Olmsted's work with the Sanitary Commission are housed in the New York Public Library.

An extensive Subject File is composed for the most part of papers relating to Olmsted's practice of landscape architecture. It contains correspondence with clients and partners, instructions to workers, progress reports, recommendations on projects, drawings, maps, pamphlets, and other material concerning the numerous parks, private estates, educational institutions, and public facilities for which he prepared landscape designs. In this series may be found information concerning the work of Olmsted's firm, which changed names and composition a number of times between its establishment in 1858 and Olmsted's retirement in 1895. (See the Biographical Note for details concerning the firm's history.)

The Speeches and Writings File includes research notes, drafts, and printed copies of speeches, articles, and other writings, some of them fragmentary. Although a major topic is landscape architecture, there are writings on other subjects, including a number of general writings and Olmsted's drafts and notes for a proposed book on the history of civilization in the United States. Autobiographical information appears in a manuscript entitled "Passages in the Life of an Unpractical Man."

The Miscellany series contains biographical material, financial and legal papers, notebooks, scrapbooks, and membership certificates in various organizations.

Prominent correspondents include Henry W. Bellows, Samuel Bowles, Charles Loring Brace, Daniel Hudson Burnham, Horace W. S. Cleveland, George William Curtis, Charles A. Dana, Edwin Lawrence Godkin, Andrew H. Green, Edward Everett Hale, William James, Clarence King, Frederick John Kingsbury, Frederick Newman Knapp, Charles Follen McKim, Charles Eliot Norton, Whitelaw Reid, Henry H. Richardson, Charles N. Riotte, Carl Schurz, George Templeton Strong, George Washington Vanderbilt, Calvert Vaux, Henry Villard, George E. Waring, Jr., and Katharine Prescott Wormeley.

Additions to the Olmsted Papers include correspondence, a diary and memorandum book, financial papers, reports, genealogical notes, newspaper clippings, printed matter, and other items dated from 1821 to 1924 but concentrated in the period of the 1880s and 1890s. The material focuses on Niagara Falls, New York, and the World's Columbian Exposition in Chicago, as well as adding information on other areas of Olmsted's career.