Board the 6 train beneath East Harlem and ride fifteen minutes south to Lenox Hill. By the time you step off, the life expectancy of the neighborhood above you has risen from 66.2 years to 89.9 — roughly six years back for every stop along the way.
Life expectancy at birth is the most compressed summary we have of how a place treats the people who live in it. It folds infant deaths and overdoses, diabetes and gun violence, asthma and despair into a single number: how long, on average, a newborn would live if their neighborhood's current death rates held for a lifetime.
The federal government has computed that number for nearly every census tract in the country — 79,626 of them in our harmonized 2020-boundary file. The national spread is enormous. But the most unsettling version of the statistic is not the gap between Mississippi and Minnesota. It is the gap you can walk.
The map below colors every census tract in New York City — and, a click away, Chicago — by life expectancy at birth. Tap any tract for its profile. The two flagged tracts in each city sit a short transit ride apart.
Census tract 106.01 covers a few blocks of Lenox Hill on Manhattan's Upper East Side. Tract 168 sits two and a half miles north, in East Harlem around 106th Street. They share an island, a subway line, a hospital system, and a borough president. Almost nothing else.
Chicago repeats the experiment with different street names. Streeterville, the high-rise district east of Michigan Avenue, and Englewood, seven Red Line stops south, are twenty-one years apart — a finding so stark that when researchers first publicized the city's tract gap it became a civic talking point.
Census-tract profiles. Income is median household income (ACS 2019–2023); upward mobility is the average adult household-income percentile of children who grew up in the tract in low-income families (Opportunity Atlas, 1978–83 birth cohorts); health measures are modeled adult prevalence (CDC PLACES 2024).
This is not a New York story or a Chicago story. Rank America's large urban counties by the spread between their healthiest and least healthy tracts — here, the 95th versus the 5th percentile, a deliberately conservative measure that ignores extreme outliers — and the gap exceeds a decade nearly everywhere.
Read the chart top to bottom and a pattern emerges: the widest fault lines run through older, highly segregated metros — Baltimore, Columbus, Dayton, Memphis, Newark, Louisville. The sunbelt counties further down are no models of equality; their spreads are simply diluted across vast suburban territory.
It is tempting to read these maps as destiny: move a family from 106th Street to 63rd and add two decades of life. That is not what the data say. Tract life expectancy describes the people who live and die there now — it bundles together poverty, smoking, housing, pollution, violence, health care, and the sorting of sick and healthy people into different neighborhoods. The number summarizes accumulated exposure; it does not assign a cause.
But the descriptive fact is the point. Two children delivered in the same hospital on the same morning, discharged to addresses fifteen minutes apart, carry statistically different lifespans home in their hospital blankets. The rest of this series is about everything that happens in between.