ZIP 21771

What ZIP 21771 actually tells you, and what it doesn't

The 21771 ZIP Code Tabulation Area reports a population of 31,653 with a median household income of $148,909, a median home value of $501,800, and median rent of $1,713 per month. The median age is 41.6 years, poverty rate 3.2%, unemployment 3.3%, and 46% of adults hold a bachelor's degree or higher. These six numbers, income, home value, rent, age, poverty, education, are the Census Bureau's most-requested per-ZCTA fields and together sketch the economic and life-stage profile of the area more reliably than any single one on its own.

A critical caveat: ZIP Code Tabulation Areas are not the ZIP codes the USPS uses for mail delivery. ZCTAs are Census geographies built to approximate the most common ZIP in each block; they can cover a slightly different footprint, omit point-address ZIPs assigned to high-volume mail recipients, and change boundaries between decennial censuses. For demographic reporting this distinction rarely matters, but for address-level applications, insurance quoting, school-zone lookups, municipal service boundaries, the ZCTA should be treated as an approximation, not as the authoritative USPS boundary.

The numbers on this page come from the American Community Survey 5-year estimates, which average data collected over 60 months. That smoothing is why ACS is durable for ZIPs with small populations but also why it lags real-time shifts, a rapidly gentrifying 21771 will show median income catching up to street-level reality two to three years after the fact. For short-horizon decisions, read these as structural context; for long-horizon decisions (buying, schooling, retirement siting), they are the stronger signal precisely because they are not noisy.