Environmental Racism: A Tool for Exploring the Enduring Legacy of Redlining on Urban Environments

Redlining was a practice beginning in the mid-1930s by which federal and local governments and financing entities denied financial services to Black people and other people of color in the United States. It is an example of government-endorsed structural racism that has had a lasting influence on mobility and wealth generation. Previous research has shown that residents of formerly redlined neighborhoods exhibit worse health, to this day, for birth outcomes, prevalence of chronic disease, health care utilization because of asthma, and cancer stage at diagnosis (Krieger, Van Wye, et al., 2020; Nardone, Chiang, and Corburn, 2020; Nardone et al., 2020; Krieger, Wright, et al., 2020); and that formerly redlined neighborhoods have more environmental hazards and fewer environmental amenities than other neighborhoods within the same city (Hoffman, Shandas, and Pendleton, 2020; Nardone et al., 2021).

To allow users to systematically investigate these disparities across multiple environmental domains, we provide an interactive interface to compare levels of a broad variety of environmental factors within historical redlining map boundaries.

Historical Context

In response to the Great Depression, the U.S. government created the Home Owners’ Loan Corporation (HOLC), with the purpose of refinancing home mortgages in default and expanding home-buying opportunities. In the 1930s, the HOLC assessed the level of security for real-estate investments in more than 200 cities across the United States. The “residential security” maps that were created categorized neighborhoods according to how desirable they were for mortgage lending. The criteria used to make these determinations included the quality of housing in the neighborhood, the recent history of sale and rent values, and, importantly, the racial/ethnic identity and class of residents living in the neighborhood. The four categories used were: “Type A (Best),” “Type B (Still Desirable),” “Type C (Definitely Declining),” and “Type D (Hazardous),” with corresponding color codes on the maps of green, blue, yellow, and red. Lending institutions utilized HOLC and similar maps to determine to whom they should lend. As a result, people who lived in “Type D” neighborhoods were denied access to mortgages and other economic opportunities. This practice became known as redlining (Gross, 2017).

Data Tool

The box plot displayed below visualizes the distribution—or spread—of data for the selected environmental indicator through a five-number summary (lower extreme, first quartile, median, third quartile, and upper extreme). For example, in the default view below, you can see the distribution of diesel particulate matter level in air across HOLC neighborhoods within Baltimore, Maryland. You can see that the median level (middle value) of diesel particulate matter across formerly “D” graded neighborhoods is higher than the median levels across all other types of neighborhoods. In fact, the median level of diesel particulate matter across formerly “D” graded neighborhoods is higher than the maximum level found in formerly “A” and “B” graded areas. Use the drop-down selectors to view the patterns for other environmental indicators and communities.

Read the tool documentation

Data Sources


  1. Gross, Terry, “A 'Forgotten History' of How the U.S. Government Segregated America,” NPR, May 3, 2017. As of January 24, 2022: https://www.npr.org/2017/05/03/526655831/a-forgotten-history-of-how-the-u-s-government-segregated-america
  2. Hoffman, Jeremy S., Vivek Shandas, and Nicholas Pendleton, “The Effects of Historical Housing Policies on Resident Exposure to Heat: A Study of 108 U.S. Urban Areas,” Climate, Vol. 8, No. 1, 2020.
  3. Krieger, Nancy, Gretchen Van Wye, Mary Huynh, Pamela D. Waterman, Gil Maduro, Wenhui Li, R. Charon Gwynn, Oxiris Barbot, and Mary T. Bassett, “Structural Racism, Historical Redlining, and Risk of Preterm Birth in New York City, 2013–2017,” American Journal of Public Health, July 2020.
  4. Krieger, Nancy, Emily Wright, Jarvis T. Chen, Pamela D. Waterman, Eric R. Huntley, and Mariana Arcaya, “Cancer Stage Diagnosis, Historical Redlining, and Current Neighborhood Characteristics: Breast, Cervical, Lung, and Colorectal Cancers, Massachusetts, 2001–2005,” American Journal of Epidemiology, Vol. 189, No. 10, 2020, pp. 1065–1075.
  5. Multi-Resolution Land Characteristics Consortium, homepage, undated. As of January 24, 2022: https://www.mrlc.gov/
  6. Nardone, Anthony, Joan A. Casey, Rachel Morello-Frosch, Mahasin Mujahid, John R. Balmes, and Neeta Thakur, “Associations Between Historical Residential Redlining and Current Age-Adjusted Rates of Emergency Department Visits Due to Asthma Across Eight Cities in California: An Ecological Study,” Lancet Planetary Health, Vol. 4, No. 1, 2020, pp. e24–e31.
  7. Nardone, Anthony, Joey Chiang, and Jason Corburn, “Historic Redlining and Urban Health Today in U.S. Cities,” Environmental Justice, Vol. 13, No. 4, 2020.
  8. Nardone, Anthony, Kara E. Rudolph, Rachel Morello-Frosch, and Joan A. Casey, “Redlines and Greenspace: The Relationship Between Historical Redlining and 2010 Greenspace Across the United States,” Environmental Health Perspectives, Vol. 129, No. 1, 2021.
  9. Nelson, Robert K., et al., “Mapping Inequality: Redlining in New Deal America,” webpage, undated. As of February 25, 2021: https://dsl.richmond.edu/panorama/redlining/
  10. NYU Furman Center, homepage, undated. As of Janaury 24, 2022: https://furmancenter.org/
  11. PRISM Climate Group, Descriptions of PRISM Spatial Climate Datasets for the Conterminous United States, Corvallis, Ore.: Oregon State University, updated November 2021.
  12. PRISM Climate Group, Oregon State University, “30-Year Normals,” webpage, undated. As of September 27, 2021: https://prism.oregonstate.edu/normals/
  13. U.S. Environmental Protection Agency, “Download EJSCREEN Data,” webpage, undated-a. As of September 27, 2021: https://www.epa.gov/ejscreen/download-ejscreen-data
  14. U.S. Environmental Protection Agency, “EJSCREEN: Environmental Justice Screening and Mapping Tool,” webpage, undated-b. As of September 27, 2021: https://www.epa.gov/ejscreen
  15. U.S. Environmental Protection Agency, “EJSCREEN: Environmental Justice Screening and Mapping Tool—Technical Documentation for EJSCREEN,” webpage, undated-c. As of September 27, 2021: https://www.epa.gov/ejscreen/technical-documentation-ejscreen