San Jose has emerged as the nation's third most dense urbanized area, at 5,914 per square mile. Virtually all development in San Jose has occurred since World War II and, as a result, San Jose is nearly all suburban (auto-oriented) and has no strong central core (downtown).

Most Dense Urban Areas: The nation's most dense urban clusters (urban areas under 50,000) are prisons. The California State Prison at Centinela is the nation's most dense urban area, at 108,600 per square mile. The Texas State Robinson Unit Prison near Abilene ranks second, at 94,600 per square mile. The third most dense urban cluster is the Garza East Transfer Facility in East Beeville, administered by the Texas Department of Criminal Justice at 57,800 per square mile. Eight of the 10 most dense urban areas in the nation were either prisons or communities in which prisons represented the overwhelming majority of the population. The highest population densities of these prisons remain well below the Sierra Club's "dense urban" and "efficient urban" population densities of more than 622,000 and 155,000 (this figure had been hastily reduced from 777,000 to 155,000). Average US urban area density is 2,400.

Most Dense Urban Areas Without Prisons: Mahanoy City, PA and Parlier, CA were the only urban clusters without prisons that had a higher population density than Los Angeles, at 8,211 and 7,846 respectively.

Little Difference in US & Canadian Urban Densities: Despite perceptions that Canadian urbanization is considerably more dense (more compact) than that of the United States, US Census Bureau and Statistics Canada data for 2000/2001 show urban areas with more than 2,500 to be only three percent more dense in Canada.