“In 1939, the government-sponsored Home Owners Loan Corporation [HOLC] produced a map of Los Angeles that would crystalize discriminatory lending practices and reinforce racial and class bias in home ownership.”
“To facilitate private investment… the federal government crafted a national set of standards for assessing mortgage risk… [T]he HOLC gathered data…and compiled the results into a rating system ranging from A to D. Communities with A ratings represented the best investments for homeowners and banks alike; B, neighborhoods that were still desirable, C, those in decline, and D, areas considered hazardous. To visually capture these rankings, the HOLC then turned these ratings into color-coded maps, using green for A, blue for B, yellow for C, and red for D – the origin of the term ‘redlining.’”
Excerpts and image from: https://www.kcet.org/shows/lost-la/segregation-in-the-city-of-angels-a-1939-map-of-housing-inequality-in-la . Similar maps of other areas in Los Angeles County can be seen at the link.