Place  /  Digital History

The Lines That Shape Our Cities

Connecting present-day environmental inequalities to redlining policies of the 1930s.

Words still matter

Federal real estate appraisers and assessors completed forms with their neighborhood descriptions for the assessed cities. Environmental terms were heavily used by appraisers when determining neighborhood classes, so it begs the question: What are the environmental conditions of historically redlined neighborhoods today?

The Digital Scholarship Lab at the University of Richmond performed a text analysis on the keywords in these HOLC forms. Researchers conducted their analysis by transcribing primary source documents, like the one above, into a database. Using the transcribed text, they were able to make the connection between environmental terms and their relationship to favorable or less favorable grade designations. Thanks to new advances in high-resolution datasets, we can thoroughly examine the environmental legacy of redlining on neighborhoods.


Environmental legacy

While many have written about the socio-economic effects of redlining, more recently researchers are using Geographic Information Systems (GIS) analysis to uncover relationships between redlined areas and environmental conditions such as tree coverage, temperature, infrastructure, and topography. This type of analysis can help identify correlations between historically redlined areas and environmental inequalities.

A recently published study shows that urban heat islands—the increase of land surface temperature due to urban design and land uses—are more intense in formerly redlined neighborhoods than in areas with other grades. It also indicates that these formerly redlined areas tend to have more impervious surfaces and fewer trees than their non-redlined neighbors.

To better understand these relationships, let’s explore four environmental factors and how they relate to redlining in the following cities:

  • Urban heat islands in St. Louis, Missouri
  • Tree canopy coverage in Montgomery, Alabama
  • Impervious surfaces in Fort Wayne, Indiana
  • Topography in Oakland, California

Urban heat islands | St. Louis, Missouri

Located on the western bank of the Mississippi River, St. Louis became a destination for many Black Americans who, during the early years of the Great Migration, were leaving the South in search of better economic conditions and opportunities in the North. 

Using satellite data, Esri cartographers analyzed temperatures across neighborhoods in the city. When comparing the average temperatures of the HOLC-designated neighborhoods, the analysis shows that the grade "A" neighborhoods had cooler averages than the neighborhoods with B, C, and D grades.

The effects of urban heat islands

Heat islands are defined by relatively higher daytime and nighttime temperatures. They also have characteristically higher levels of air pollution, result in higher energy bills, and create uncomfortable living conditions that can lead to heat-related illness, chronic respiratory symptoms, and even pre-term birth. During summer months, St. Louis temperatures can reach well over 90° F with high humidity, which can lead to illness or even cause death.

If you compare the adjacent maps below, you can see how heat islands relate to the urban landscape and the historic HOLC zones. Pay particular attention to the locations of city parks and their relative temperatures. Alternatively, explore areas that are more industrial—namely those along the Mississippi river where temperatures are relatively warmer.