Established as part of the New Deal, the Home Owners' Loan Corporation offered mortgage loans to expand home buying. In the process it made a detailed grading of neighborhoods into categories A (green) to D (red), with important long-term consequences on racial discrimination.
I am interested in the description of the C (yellow) category:
The Third grade or C areas are characterized by age, obsolescence, [...]. "Jerry" built areas are included as well as neighborhoods lacking homogeneity.
My questions are: what is/was a "Jerry" built area? Were they a direct consequence of the Great Depression? And why would they automatically get graded C?