Residential Zoning by Race:
How Pittsburgh’s Zoning Districts Promote Different Housing Options for Black and White Residents
Part 5: The Redlining Factor
by Carolyn Ristau
Redlining as a Factor Influencing the Location of Residential Zoning Districts
Ten years after Pittsburgh adopted its first exclusive single-family zoning district, the Home Owner’s Loan Corporation (HOLC) issued its Residential Security Map that graded residential areas A, B, C, or D, with A as best, for Pittsburgh and its vicinity as part of a series of over 200 maps across the country.
Green = A “Best”
Blue = B “Still Desirable”
Yellow = C “Definitely Declining”
Red = D “Hazardous”
The HOLC maps are commonly referred to as “redlining” maps because of the red color used to mark the areas HOLC identified as the riskiest for investment. The unequal impacts of the HOLC maps on metropolitan areas across the country is well documented, included on the Mapping Inequality project led by the University of Richmond’s Digital Scholarship Lab. Mapping Inequality is the source of the HOLC data used throughout Residential Zoning by Race.
There is a strong correlation between Pittsburgh’s single-family zoning districts and areas graded A “Best” and B “Still Desirable” and the City’s multi-family zoning districts and areas graded C “Definitely Declining” and D “Hazardous.” The following series of maps illustrates this correlation across the 1927, 1967, and 2021 zoning maps.
Redlining and Single-family Zoning Districts 1927-2021
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1927 Single-Family Districts & Redlining
87% of the single-family zoning districts established in 1927 were graded by HOLC in 1937.
99% of the graded single-family zoning districts are in A “Best” and B “Still Desirable” areas.
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1967 Single-Family Districts & Redlining
70% of the single-family zoning districts in 1967 were areas graded by HOLC in 1937.
62% of the graded single-family zoning districts are in A “Best” and B “Still Desirable” areas.
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2021 Single-Family Districts & Redlining
82% of the single-family zoning districts in 2021 were areas graded by HOLC in 1937.
46% of the graded single-family zoning districts are in A “Best” and B “Still Desirable” areas.
Redlining and Multi-Family Zoning Districts 1927-2021
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1927 Multi-Family Districts & Redlining
72% of the 1927 multi-family zoning districts were graded by HOLC in 1937.
64% of the graded multi-family zoning districts were identified as C “Definitely Declining” and D “Hazardous.”
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1967 Multi-Family Districts & Redlining
93% of the 1967 multi-family zoning districts were areas graded by HOLC in 1937.
77% of the graded multi-family zoning districts were identified as C “Definitely Declining” and D “Hazardous.”
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2021 Multi-Family Districts & Redlining
88% of the 2021 multi-family zoning districts were areas graded by HOLC in 1937.
71% of the graded multi-family zoning districts were identified as C “Definitely Declining” and D “Hazardous.”
Zoning and Redlining Summary
As these maps show, there is a strong relationship between the location of 1927 single-family zoning districts and areas that were graded A “Best” and B “Still Declining.” This relationship drops by 2021. However, the relationship between the location of multi-family zoning districts and areas that were graded C “Definitely Declining” and D “Hazardous” remains strong across all three years of zoning maps.
