Most of the counties where people live longest are either sparsely populated or well-to-do suburbs of large cities.
Forty-seven of the counties listed have a population of which the largest racial component is non-Hispanic whites.
[1] Counties with the longest life expectancy are located in 21 states: Colorado (11); California and Iowa (5); Nebraska (4); North Dakota, Virginia, and Minnesota (3); Alaska, New York, and New Jersey (2), and Texas, New Mexico, Wyoming, Florida, Michigan, South Dakota, Idaho, Maryland, Utah, Wisconsin, and Oregon (one each).
[1] The residents of three adjacent counties in the high-elevation Rocky Mountains of Colorado have the longest life expectancy.
[3] A study published in the Journal of the American Medical Association in 2016 concluded that income was a major component of the difference in life expectancy in states, counties, races, and regions of the U.S.. Men in the richest one percent of the population lived 15 years longer than men in the poorest one percent of the population and women in the richest one percent of the population lived 10 years longer.