Census ACS 5-Year · 500 counties
Densest US Counties by Population per Square Mile
New York County (Manhattan) is the densest US county at over 70,000 people per square mile, followed by other New York City boroughs and a handful of dense urban counties in California, New Jersey, and Massachusetts. Density at the county level reveals the structure of metropolitan areas: dense urban cores surrounded by less-dense suburban counties. Dense counties have outsized economic productivity per square mile, lower per-capita carbon footprints, and more public transit, but also higher housing costs and stronger political-economic divides with surrounding regions.
Key Findings
- 1New York County, NY leads with a people per square mile of 71842 / sq mi, followed by Kings County, NY (38144 / sq mi) and Bronx County, NY (33651 / sq mi).
- 2Placer County, CA ranks last at 293 / sq mi, while New York County, NY leads at 71842 / sq mi.
- 3The national median across all states is 706 / sq mi (San Lorenzo Municipio, at the midpoint).
- 4The top 10 states are: New York County, NY, Kings County, NY, Bronx County, NY, Queens County, NY, San Francisco County, CA, Hudson County, NJ, Suffolk County, MA, Philadelphia County, PA, District of Columbia, DC, Alexandria city, VA.
Full Ranking: Densest US Counties by Population per Square Mile
Source: Census ACS 5-Year Estimates
Methodology
Rankings are based on American Community Survey (ACS) 5-Year estimates from the US Census Bureau. All 50 states and the District of Columbia are included. The ACS surveys approximately 3.5 million households annually and provides detailed demographic, social, economic, and housing data. 5-Year estimates offer the most reliable data for state-level comparisons by averaging responses over a 60-month period. Percentages may not sum to 100% due to rounding.
More US Counties Rankings
Explore Other Rankings
Frequently Asked Questions
New York County, NY has the highest people per square mile at 71842 / sq mi, according to latest Census ACS data. Kings County, NY and Bronx County, NY round out the top three.
Placer County, CA has the lowest people per square mile at 293 / sq mi. Marion County, OR is second-lowest at 293 / sq mi.
The median across all 500 states is 706 / sq mi. Note that the national median and the state-level median are calculated differently, the state median represents the midpoint when all states are ranked.
This data comes from the American Community Survey (ACS) 5-Year estimates published by the US Census Bureau. The ACS surveys approximately 3.5 million households annually and provides the most comprehensive demographic data available between decennial censuses.
Rankings are based on the latest available Census ACS 5-Year estimates. The Census Bureau releases new ACS data annually. Our data was last updated on April 12, 2026.
Rankings are based on American Community Survey (ACS) 5-Year estimates from the US Census Bureau. All 50 states and the District of Columbia are included. The ACS surveys approximately 3.5 million households annually and provides detailed demographic, social, economic, and housing data. 5-Year estimates offer the most reliable data for state-level comparisons by averaging responses over a 60-month period. Percentages may not sum to 100% due to rounding.