It’s not considered one of the “traditional” genealogy record groups, but Record Group 33, Records of the Extension Service, is a treasure trove of information about farm life across the United States from about 1910 to 1950 or so. Even if one’s own ancestors are not mentioned in the records, they provide excellent county-level context on rural life. I lectured on these records on the 2011 NARA genealogy fair and have written about them a couple times, as well. My research guide, “Agricultural Extension Service Annual Reports, 1909-1968, and Related Records“ will help you get started.
NARA is working on digitizing the the Service’s microfilmed annual reports (ca. 1908-1944) so they are not yet available online. I am delighted to report, however, that nearly 350 motion picture films from RG 33 have been digitized and are available for viewing or download from the National Archives Catalog. (Some may be restricted by copyright or other intellectual property right restrictions.) Happy viewing!