The Peggy Clark Papers span the period 1880-1997 with the bulk of the materials dating from 1936-1970. Contents include light plots, scenic renderings, blueprints, correspondence, published and unpublished writings, programs, photographs, posters, scripts, scrapbooks, clippings, notes, audio cassettes, and memorabilia.

The Project Files series forms an all-encompassing assemblage of materials that chronicles Clark's career as an amateur and professional designer of theatrical lighting, scenery, and costume. It is subdivided into four subseries. The first, "Stage Productions" contains an alphabetical and dated list of Broadway musicals, plays, revues, and dance recitals. Materials for each title are thematically arranged (lighting, contracts, props, etc.) within storage containers to mirror the organization of Clark's original production notebooks. These can and often do include oversized lighting plots, scenic renderings, posters, and costume sketches. Many also contain setting and costume fabric swatches, photographic negatives, and delicate drawings and sketches in a variety of artistic mediums: pencil, ink, charcoal, acrylic, and watercolor. The types and quantities of materials available for a given title varies considerably depending on Clark's degree of involvement with that production.

Lighting and setting materials represent the most voluminous components of the notebooks. These consist principally of rolled plots and diazotype reproductions, blueprints, cue sheets, sketches, equipment specifications, and notes. Clark's close working relationship with set designer Oliver Smith is clearly evident in these materials, many of which feature holograph drawings in Smith's hand or Clark's drawings of prominent Smith designs. Correspondence included under the titled productions represents only those documents originally found with the production notebooks. Researchers are encouraged to examine the general Correspondence series for additional correspondence of possible relevance. Individual titles may also include any of the following: clippings, contracts, black and white or color photographs, general production notes (schedules, expenses, etc.), programs and invitations, and annotated and unannotated scripts.

The "Industrial Productions" subseries consists almost exclusively of lighting projects done for private American manufacturers, special interest groups, or the U.S. government. Materials are arranged by corporate name and mirror the internal structure of the stage production files. Of particular interest are Clark's files for the Weirton Steel Co. Labor Day pageants from 1942-1944, a series of festivals celebrating the achievements of the American home front and the armed forces. "Theater Specifications" is a subseries of individual and composite drawings of prominent performing arts venues throughout the United States. The "Miscellaneous Projects" subseries rounds up an assortment of relatively small-scale lighting and design projects from various points in Clark's career. Highlights include materials for the radio show and the opening of the Tomb of the Unknown in Washington, D.C.

The Writings series is comprised of over thirty typescript articles, plays, journals, scenarios, illustrated works, a novel, and other literary pieces that document Clark's professional and private interests in the theater. The most substantial of her unpublished personal works are the novel (1939) and her tirelessly re-worked musical (1964). (1965) and (1944) are exercises in illustration and political activism respectively, while (1958) provides a somewhat surreal example of her unique narrative style.

The Correspondence series contains chronologically arranged letters to and from family members, friends, and colleagues. Eleanor Linton Clark, Lloyd R. Kelley, and friend Vicky Glaser are frequent correspondents. Many of these letters, by virtue of the recipient's personal interests, contain references to current theatrical productions and upcoming tours. Peggy Clark's life-long fondness for her summers at Woods Hole, Mass. permeates much of this writing and contextualizes the longer literary works, paintings, and photographs that exhibit similar themes. The series also contains scattered correspondence from Oliver Smith, Edwin Lester, and other prominent figures in American theater.

The Organizational Materials series consists of correspondence, meeting minutes, promotional materials, and other content related to Clark's associations with professional technical theater organizations, most notably the United States Institute for Theatre Technology, and United Scenic Artists.

The remaining series form a veritable collage of Clark's personal and professional life. The Photographs series contains a chronological run of portraits, as well as images of the Clark family and its beloved French bulldogs. The Drawings series contains an eclectic mix of Clark's non-theatrical drawings, including sketches and paintings created mainly for graduate school assignments. In addition, there are childhood drawings, sketchbooks of Woods Hole scenery, and a humorous series of original Christmas cards. Scrapbooks in the collection consist of several bound volumes of photographs, clippings, programs, and memorabilia related to events at Smith College. A small series of Biographical Materials contains resumés and clippings about Clark and her professional activities, as well as documents related to family history. The final Miscellany series contains an assortment of union stamps and other items associated with theater production.