Coastal cities like New York, Washington, San Francisco, Boston and Los Angeles do exhibit close ties to one another, showing that people in counties with similar incomes, education levels and voting patterns are more likely to be linked. But nationwide, the effect of such similarity is small. And the pull of regionalism is strong even for major cities. Brooklynites are still more likely to know someone on Facebook near Albany or Binghamton than in the Bay Area…

State lines are powerful boundaries in binding nearby places. For many counties, as the maps illustrate, the likelihood of friendship drops off sharply at state borders. And counties within a given state tend to be strongly connected to one another. This is particularly striking in Michigan, where counties near the Indiana and Ohio state line are more closely tied to Michigan’s Upper Peninsula than to out-of-state counties closer by…

History is another significant force in shaping these networks. Decades-old migration patterns can help explain why some distant counties are disproportionately connected today. Northern cities like Chicago and Milwaukee still retain close ties to Southern counties along the Mississippi River, where African-American workers who were part of the Great Migration starting a century ago left communities for industrial jobs in the North…

In other parts of the country, physical geography forms a kind of social barrier. Friendship links from Belmont County, Ohio, extend east but don’t cross the Appalachian Mountains in Pennsylvania or the Blue Ridge range in Virginia. In Scott County, Ark., friendships do cross state lines, into Oklahoma, Louisiana and Texas. But they don’t cross the Mississippi River to the east. In Nassau County, N.Y., the likelihood of friendship links declines steeply off Long Island…

Other county outliers in the data can be explained by distinct roles some communities serve: Onslow County, N.C., which is connected to much of the country, is home to Marine Corps Base Camp Lejeune.

Based on the map of DuPage County plus discussion of the broad patterns, here is what I notice about the Chicago collar county:

1. More ties in the other suburban counties and then within Illinois.

2. There are a number of Midwestern ties spread across adjacent states.

3. DuPage County has more distant ties to a few other places. I’m guessing Florida and Arizona show up as retirement destinations. Both Summit County, Colorado and Teton County, Wyoming show up – are these popular vacation destinations? (Both of these counties have relatively small populations.)

4. There are not many ties to the Northeast though other metropolitan areas show ranging from Seattle to Los Angeles to Las Vegas to Nashville.

On the whole, DuPage County is pretty wealthy and I would guess fairly mobile. The Facebook connections by location might support that though there are still many Chicago area and Illinois relationships.