Four O'Clock Factoid is a daily feature on Track Twenty-Nine helping to get you through the workday with a bit of useless knowledge.
New York County, synonymous with the borough Manhattan, is the most densely populated county in the United States. In 2008, the average density of Manhattan was 71,201 persons per square mile. However, Manhattan is not the most populous of New York City's five boroughs. That distinction goes to Brooklyn.