The expansion of water and sewage infrastructure across urban areas leads to a significant increase in Black life expectancy between 1900 and 1940. Montag (2019) writes: "While waterworks systems decreased mortality for all races... Black Americans—particularly those who resided in cities—benefited more than whites from waterworks systems, as they were less likely to be able to afford private sources of clean water before these systems were built and thus were more susceptible to disease."

At this time, segregation is largely limited to house by house and block by block. Few Black families live in urban neighborhoods that are more than 20 percent Black.