Our lives are heavily shaped by two points of geography: where we live and where we work. Those locations determine how long we spend commuting, how we plan our errands, where and with whom we socialize (admit it — you've turned down a dinner invite because it just wasn't on your way home).

Add up all of these daily trips across thousands or millions of people, and commuting patterns shape whole metropolitan areas, too. They determine where congestion occurs, how we invest in infrastructure and housing, and how populations ebb and flow over the course of the day. Take Manhattan: A borough of about 1.5 million people, the island swells most days to a daytime population that's twice as large, thanks to commuters.

The above map, based on new five-year American Community Survey data released last week, illustrates these commutes for the 38 million Americans who leave the counties where they live when they head to work most days. In the District of Columbia, for instance, about 95,000 workers come in each day from Fairfax County. Nearly 140,000 do from Prince George's County.


As for workers traveling in the other direction, from the District to Prince George's? That's only about 15,600 commuting against the crowd.

The Census Bureau produces these numbers using a question in the American Community Survey that's both precise and limiting: "At what location did this person work last week?" The answers are paired against respondents' home locations to draw a picture of commuting flows.

That means the data mapped above may also capture a D.C. resident who went to a convention in Chicago the previous week, or a long-distance trucker who lives in California but spent that week driving across Ohio. So many of the far-flung county pairs above don't reflect infamous "super-commuters," people who spend several hours a day on Amtrak, or who log their commutes in airline mileage.

Rather, click on a place like Cook County, Ill., home of Chicago's major convention center and several corporate headquarters, and you'll get a sense of its economic pull: People from all over the country spent time working there the week in question, even if they don't make that trip every day.

This picture no doubt, though, does capture workers with epic commutes: people from all over the upper Great Plains who spend Monday through Friday each week at lucrative fracking jobs in McKenzie County, North Dakota, or oil-industry hands who fly back and forth to Alaska's North Slope, or workers in the District who'd rather buy the bigger home they can afford in Pennsylvania.


In the aggregate, this map tell us that most of the District's workers don't actually live in the District — 70 percent commute in from outside of it, the highest share among large counties in the U.S. In contrast, nearly all of the workers in Clark County, Nev. — home of Las Vegas — do live there. Just three percent of the county's workers come from beyond the county, which is surrounded by desert.


All of this data also tells us that Dallas County has a much larger geographic footprint than Travis County (home of Austin). Meanwhile, a city like Atlanta (Fulton County), the largest jobs center in the South, pulls in workers from a wide radius. Its metropolitan area, defined here by where workers come from, appears to stretch into Alabama and South Carolina:


And then there's a place like Harney County, which looks like this, an isolated economy in the middle of Oregon bypassed by Interstates and home to no major cities: