This 1933 map of Birmingham, Alabama, demonstrates the color-coding system10 used by the HOLC to determine the riskiness of making loans for properties in certain neighborhoods. Wealthy White neighborhoods were marked in green and given an A (“best”) grade as the safest investments. Blue B neighborhoods were deemed “still desirable,” although less so, whereas neighborhoods with a lot of recent immigrants might get a yellow C (“declining”) grade. Low-income, ethnically diverse neighborhoods were outlined in red and rated D (“hazardous” to lenders). This particular map includes an additional designation separate from the HOLC system: solid gray for areas with a “Negro concentration.” Cross-hatching indicates industrial and commercial areas, and diagonal lines indicate undeveloped property. Image: Courtesy U.S. National Archives.