The University of California Cooperative Extension (UCCE) Modoc County Records span the years 1929–2011, with the bulk of the materials dating from the mid-1940s through the 1990s. The collection documents the agricultural, educational, and community outreach work of UCCE in Modoc County and northern California. Materials include annual reports, administrative files, agricultural and rangeland research, watershed and habitat studies, audiovisual media, 4-H programming, and correspondence. Annual reports prepared by farm advisors provide statistical summaries, detailed narratives of project activities, research results, and plans for future programs. Administrative files contain agricultural reporting, extension work, professional activities, crop and livestock assessments, newsletters, correspondence, and presentation drafts, particularly from the 1940s through the 1990s. Series 3 consist of Ranch and Range Management Records relating to agricultural, rangeland, and livestock management include data, reports, correspondence, and case studies on beef cattle production, pest and parasite control, disease management, land management, and ranch operations. Series 4 consist of watershed conservation and aquatic habitat monitoring highlight collaborative projects in the Goose Lake Basin and surrounding watersheds. These records include project designs, implementation reports, oversized drawings and blueprints for restoration and infrastructure improvements, water quality monitoring, fish population studies, and detailed research on native species. Series 5 consist of 4-H records. Series 6 consist of Audiovisual materials include reel-to-reel tapes, cassette tapes, videotapes, photographic prints, negatives, and slides. Photographs and slides were used in publications, outreach efforts, and farm advisor presentations. Together, these records illustrate the history of Cooperative Extension’s role in shaping agricultural practices, natural resource management, and rural community life in Modoc County.