Greenfields: former agricultural lands laying in fallow. Greenfields proliferated during the early 20th century, as agribusiness consolidated and small farms were abandoned.
Brownfields: former industrial lands, frequently with pollution hazards. Brownfields proliferated during the late 20th century, as manufacturing businesses moved overseas and firms abandoned domestic factories.
Redfields: former middle-class neighborhoods, frequently characterized by strip malls, tract housing, and other properties that are now "in the red" and owned by absentee financial institutions. Redfields have proliferated in the first decade of the 21st century, in the wake of the real estate bubble, as the suburban middle class succumbs to crushing debt and poor access to economic opportunity.