Explore this interactive map of racial change in Hartford County, Connecticut, which displays the percentage of the "White" population in towns and census tracts from 1900 to 2018. Since categories of race and ethnicity are socially constructed, US Census labels vary over time. For example, "Native White" and "Foreign-born White" were combined and generally reported as "White" by the 1940s, and "Negro" was replaced by "Black" in 1980. While the Census classified "Mexican" as "Other races" in 1930, it moved this group back to "White" in 1940, and began to report "Puerto Rican or Spanish surname" data in 1960, followed by "Hispanic or Latino" in later decades, as an ethnic category regardless of race. Beginning in 2000, the Census allowed people to select more than one racial category. To create this century-long map that visualizes patterns across racial and ethnic categories that vary over time, we decided to show the percentage of the "White" or "White alone (non-Hispanic)" population with uniform shading for each area, along with data details for specific years in the hover box. Map developed by Ilya Ilyankou and Jack Dougherty, with contributions by Katie Campbell and UConn MAGIC. View source data and code on GitHub. Learn more at OnTheLine.trincoll.edu.