Farmland did OK during the 70s.
Illinois is mostly corn/soybeans.
Valuation change for Illinois farmland:
1971 ... 0.2%
1972 ... 7.3%
1973 ... 12.0%
1974 ... 33.6%
1975 ... 7.4%
1976 ... 25.5%
1977 ... 37.3%
1978 ... 11.5%
1979 ... 14.3%
Add another 2-3% per year for net cash rent yield.