Here are the youngest and oldest counties in the US

The median age of residents in US counties and county equivalents ranges from just 22.4 years in Lexington City, Virginia, to 66.6 in Sumter County, Florida.

The US Census Bureau recently released data on the age breakdown of the US population. Among the various pieces of information were estimates for the median age of the residents in each of the 3,142 counties and county equivalents across the country.

Although there is a lot of variation in age within each state, there are a few interesting trends. Far northern counties in Maine, Michigan, and Wisconsin tend to have older populations, as do popular retirement destinations in Florida. Meanwhile, counties in the Southwest and in oil-rich areas in North Dakota and Texas have some of the lowest median ages in the country.

Here's a map illustrating the estimated median age of residents in each of those counties as of July 1, 2015. Lighter counties are younger, and darker counties are older:

Business Insider/Andy Kiersz, data from US Census Bureau

And here are the 15 counties with the youngest and oldest residents, along with their median ages:

Business Insider/Andy Kiersz, data from US Census Bureau

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