At the turn of the previous century, growing concern over the quality of life for rural Americans prompted President Theodore Roosevelt to appoint a Commission on Country Life in 1908. One of the direct outcomes of the Commission's recommendations was the passage of the Smith-Lever Act in 1914, which established a national extension service to place the knowledge generated at land-grant universities into the hands of farmers and rural citizens. The Agricultural Extension Service formalized and built upon existing efforts of land-grant universities to enhance the knowledge of farmers and apply scientific discoveries for improved agricultural practices.

Beginning in 1913, the Agriculture Extension Service, later known as UC Cooperative Extension, placed farm advisors employed by the University of California in every county that formed a farm bureau and agreed to sponsor Extension Service work. While arrangements have evolved, advisors continue to work in all California counties today and address problems ranging from soil conditions and land reclamation to irrigation; from livestock breeding to improved varietals; and from mechanization to disease and pest management, to enable farms to increase efficiency and productivity.

In 1915, the University of California established a branch in San Diego County. Cooperative Extension staff conduct educational programs through individual consultation, meetings, farm and home demonstrations, field tours, industrial and governmental relations, newsletters, and the news media.