Ten million Americans pack up their lives and move to another part of the country every year. But where are they moving to? The University of Wisconsin-Madison has made an interactive map that tracks the net migration to different counties across the U.S.

The map uses data sets that include age, race, Hispanic-origin, and sex to trace migration patterns from 1950 to 2010. Purple means that more people are moving to a county, and orange means more people are moving away from a county.

Over the past ten years, the counties seeing the biggest gains are in southwestern Nevada, western Arizona and pretty much all of Florida. (On the real map you can also see Alaska and Hawaii. Hi, Alaska and Hawaii! Sorry!) This is most likely due to Americans who are living longer, and moving to these places to retire. If I choose only to highlight the migration patterns for 54- to 74-year-olds, it becomes obvious:

The coolest thing is playing with the data on the website, where you can cut and slice the data between counties and start to see some trends up close, especially when it comes to the age of who is moving. Just looking at some of those dark purple counties on a chart (St. Lucie in Florida, Nye in Nevada, and Mohave in Arizona), confirms the boomer population boom:

Whoa. Some of these areas also have growth in the young, family-producing range, but you can see a clear bump around the retirement age, as these warm, sunny counties welcome their new grey-haired residents.

It feels like everyone I know is moving to Austin, Texas, so I plugged in the county for Austin (Travis County), and, for comparison, Brooklyn, New York (Kings County); and Portland, Oregon (Multnomah County) over the last 30 years or so:

You can see a clear spike in each city where young, impressionable 20- and 30-somethings are moving to town, but especially in Austin where they’ve arrived in ridiculous numbers. Brooklyn and Portland’s new residents skew a little older, but they’re still coming.

It’s also interesting to look at places that have seen negative migration patterns, like Detroit, Michigan (Wayne County); St. Louis, Missouri (St. Louis City County); and Buffalo, New York (Erie County):

More people have almost uniformly moved away from these counties in the last few decades. The one big exception is in St. Louis, which is now gaining 20-somethings at rates that look more like Brooklyn’s growth for the same age range.

I added a few more decades, going all the way back to the 1950s for more perspective:

Here, when you can see the trends over time, you can really witness the dramatic changes in St. Louis, which was bleeding 30-somethings in the ’50s, ’60s and ’70s, but now gaining younger folks. The news is not as good in Buffalo, which was once a somewhat popular destination with the same age group, but not anymore.

Of course, one thing to remember is that counties come in all shapes and sizes and can encompass an entire metropolitan area, carve up a big city, or be much, much larger than the urbanized areas within them. And of course, these don’t take into account how people move within counties, from city to suburb, for example. But as a method of measuring the comings-and-goings of Americans, it’s a pretty awesome way to look at where we choose to live.

Via Gizmodo