The most populous counties in the U.S. mapped

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According to the most contemporary U.S. Census Bureau, Los Angeles County in California is the most populous county in the country, with a total population of more than 10 million. Cook County in Chicago follows. It has almost 50% of Los Angeles County’s population, with five million residents. In Texas, Harris County, Maricopa County in Arizona, and San Diego County and Orange County in California have populations above three million.

There are 45 U.S. counties with a population grater the one million.

U.S. Counties with a population of over 1 million

Largest population U.S. counties nationwide (2019)

1. Los Angeles County (California) – 10,039,107
2. Cook County (Illinois) – 5,150,233
3. Harris County (Texas) – 4,713,325
4. Maricopa County (Arizona) – 4,485,414
5. San Diego County (California) – 3,338,330
6. Orange County (California) – 3,175,692
7. Miami-Dade County (Florida) – 2,716,940
8. Dallas County (Texas) – 2,635,516
9. Kings County (New York) – 2,559,903
10. Riverside County (California) – 2,470,546

Over the next 40 years, the number of counties with over 1 million citizens is projected to increase by 29.

U.S. counties with a population of over one million: past, present, and future

In comparison, the number of counties with a population of over 100,000 is 488.

U.S. Counties with a population greater than 100,000