Iowa State has a PhD program in Agricultural History and Rural Studies!

The program is designed as a Ph.D. program, but students without an M.A. in history will be expected to qualify for the departmental M.A. in history while progressing toward the doctorate. In some cases, the M.A. may be recommended as the terminal degree. Thirty semester hours of graduate credit are required for the M.A. and 72 for the Ph.D. Students who continue beyond the M.A. are expected to pass a qualifying examination in their general field of study and preliminary examinations in three areas of specialization, complete a dissertation, and defend it orally in the Ph.D. final examination.
Quick Facts:
The Agricultural History and Rural Studies Program (AHRS) is the only focused agricultural and rural history doctoral program in the United States. The program, however, defines agricultural and rural history broadly, to include a number of areas of faculty and student interest.
AHRS generally enrolls about a dozen students, at various stages of their doctoral program.
Recent dissertations have included studies of the development of agricultural communities in California, the creation of farm safety programs in the mid-twentieth century, adoption of technological and scientific innovation by mid-twentieth century midwestern farmers, and work, family and community in communal societies.