US Counties With the Highest Population Aged 18 and Over

3,142 US counties ranked by population aged 18 and over, from highest to lowest. First are Kalawao County, HI (1744.19), Petroleum County, MT (1132.17) and Yakutat City and Borough, AK (1096.84). The middle one of the 3,142 has 784.47.

What this measures

The number of residents aged 18 and over. The PLACES health percentages are shares of this group. Source: CDC PLACES.

This is a count, so it is ranked per 1,000 residents. Ranked by the raw total, it would just list the biggest counties.

For most measures, a national ranking mostly sorts places by income and by how urban they are. Each county’s own page compares it with the 50 counties most like it instead, which is often the fairer view.

The 100 highest counties

More on population aged 18 and over

• US Counties With the Lowest Population Aged 18 and Over
• Population aged 18 and over by US county: map by year and what it goes with

A ranking describes places, not the people in them, and a high or low place does not by itself say why. All US rankings.