Mapping Segregation: Redlining, Racial Covenants, and GIS Analysis

A story has circulated in my family for years: my Black, West Indian grandparents, renters in New York’s Lower Hudson Valley, were unable to purchase the home they lived in. According to family lore, the White family my grandmother worked for acquired the house using my grandparents’ funds and later transferred ownership to them. The details remain uncertain, but such arrangements would not have been unusual in many parts of the United States during the first half of the twentieth century. Motivated by both personal history and professional curiosity, I began investigating how housing discrimination manifested spatially across the country.

If you reside in the United States, chances are your neighborhood bears the imprint of early twentieth-century racial and economic segregation. While cities today often present as racially and ethnically diverse, closer examination at the neighborhood scale reveals enduring patterns of separation. Urban cores may appear integrated at a macro level, yet when analyzed spatially, many remain divided along racial and socioeconomic lines. Geographers have long sought to explain these spatial disparities—why wealth clusters in certain areas, why communities of color were historically confined to specific neighborhoods, and how these divisions persist. Maps have been central to both the creation and analysis of these patterns.

Racial Covenants and the Architecture of Exclusion

In the early 1900s, racially restrictive covenants became embedded in property deeds throughout the United States. These legal clauses prohibited Black residents, Asian Americans, Jewish families, immigrants, and other marginalized groups from purchasing—or in some cases even occupying—homes in designated neighborhoods. These covenants were not isolated anomalies; they were widespread instruments shaping residential geography.

Home finncing at the time relied heavily on private capital and cash transactions. In 1933, during the New Deal era, the Home Owners’ Loan Corporation (HOLC) was established to stabilize the housing market and prevent foreclosures. To guide lending decisions, HOLC assessors produced “Residential Security” maps in major cities. These maps classified neighborhoods according to perceived investment risk.

Areas labeled “A” and shaded green were considered the most secure, typically composed almost entirely of White residents. “B” (blue) and “C” (yellow) neighborhoods reflected varying mixes of White residents and immigrants with higher economic standing. “D” zones—colored red and deemed “Hazardous”—were predominantly Black communities. These classifications heavily influenced lending behavior, with red-designated neighborhoods often denied loans or offered mortgages under unfavorable conditions. The term “redlining” emerged from this practice and remains central to discussions of housing inequality.

Research by the National Community Reinvestment Coalition indicates that nearly three-quarters of neighborhoods graded as “Hazardous” in the 1940s remain low-to-moderate income today. Additionally, approximately 64% of those historically redlined areas are now majority-minority communities. Such findings are supported by contemporary mapping initiatives that digitize and analyze historical records.

GIS as a Tool for Historical Accountability

Modern geographic information systems (GIS) have become instrumental in documenting and visualizing housing segregation. Prologue DC leads a long-term effort titled “Mapping Segregation in Washington DC.” This project identifies properties with racial covenants and presents the data through interactive maps, illustrating how discriminatory housing practices shaped residential patterns, schools, playgrounds, and public infrastructure.

Similarly, University of Minnesota hosts the “Mapping Prejudice” project, which systematically identifies racially restrictive covenants within Minneapolis property records. These initiatives transform archival documents into accessible spatial narratives, making structural racism visible in ways that written records alone cannot.

As the “Mapping Prejudice” project emphasizes, the material and psychological consequences of redlining are often less visible to those who have not personally experienced discrimination. By presenting historical injustice through interactive mapping, GIS projects bridge that awareness gap and contextualize ongoing disparities.

Data Gaps and Research Barriers

Despite technological advances, uncovering the full extent of housing discrimination remains challenging. Sarah Shoenfeld of Prologue DC notes that Washington, DC deed records have only been digitized back to 1921. Earlier records exist but require funding and administrative prioritization to become publicly accessible. Digitization efforts depend largely on limited office budgets supported by service fees, constraining progress.

These limitations are not unique to the nation’s capital. In Richmond, Virginia, data management specialist Harry Samuels explored how neighborhood “disamenities”—such as vacant lots, abandoned buildings, and blight—affect housing prices. Using spatial regression analysis, he sought to quantify the relationship between proximity to disamenities and property values, particularly in communities of color.

However, the analysis was complicated by inconsistent geographic scales and incomplete datasets. Some variables were available at the Census Block Group level, others at the Census Tract level, making precise modeling difficult. Even so, Samuels identified correlations between historically redlined neighborhoods and present-day concentrations of disamenities, reinforcing findings that discriminatory housing policies have long-term economic consequences.

Researchers investigating population data frequently encounter similar challenges. Historical maps may exist only in paper form, be limited to specific years, or remain undiscovered in archival storage. The uneven availability of granular spatial data complicates efforts to trace systemic inequities across decades.

Personal History, Public Geography

I have yet to confirm whether my grandparents’ home carried a racial covenant or fell within a redlined district. Evidence suggests that discriminatory lending practices operated in their region, but accessing detailed archival records remains difficult from afar. Without comprehensive digital repositories similar to those maintained by the University of Minnesota or Seattle Civil Rights & Labor History Project, verification requires time, travel, and institutional cooperation.

Until then, the family story remains anecdotal—but it exists within a broader, well-documented national pattern. Through GIS and historical mapping, we now possess tools capable of illuminating those patterns with precision.

Understanding redlining and racially restrictive covenants is not solely about revisiting the past. It is about recognizing how spatial policies shape generational wealth, neighborhood composition, and opportunity. Maps once used to exclude are now being repurposed to reveal, analyze, and educate.