The Residential Security Maps, drawn by the Federal Government in 1940, categorized urban housing markets across the country according to their perceived value. The maps, simultaneously, were: 1- a policy framework intended to measure investment risk, 2- an articulation of ideology, particularly a racist, segregationist one, and 3- a reflection of urban conditions at the time the map was drawn. It can be hard to distinguish the degree to which the grades on the map represent ideologically-driven discrimination versus actual housing conditions. For instance, African-American migrants to Pittsburgh were largely relegated to the lowest quality housing as a function of racism in both housing and labor; it is hard to assess, from available data, whether the communities where African Americans lived were overwhelmingly included in the lower grades because of the racial composition or because of the quality of the neighborhoods they were limited to. While much of the research about HOLC has attempted to address this question, to some extent, this kind of question is really just an exercise in splitting hairs.
The Residential Security Map of Pittsburgh adds more nuance about housing conditions in Pittsburgh to the available census data. The first chart illustrates the presence of African Americans in Pittsburgh's neighborhoods. The neighborhoods are grouped by the grade they received on the HOLC map. Green and Blue areas were considered to be valuable and wise for investment while Red and Yellow areas were considered to be unfit, degraded, and at the "end of their productive use." Setting aside the groupings and taking the chart overall, it is clear that a handful of spaces in Pittsburgh were almost entirely occupied by African Americans (the circles near the top of the chart) while vast majority of spaces were almost entirely occupied by whites (those at the very bottom--the thick black lines are the medians of each group meaning that half of the neighborhoods are below that line). The dashed blue line represents the overall share of African Americans in Pittsburgh in 1940. Many neighborhoods, regardless of their value or conditions, were exclusively, or nearly exclusively, white. Comparing the groupings between one another, it is clear that communities with heavy concentrations of people of color were consistently considered without value and undeserving of investment. This reflective both of an ideology that did not value integrated neighborhoods and of the poor housing conditions that African Americans were limited to.