I watched an episode of the terrible sitcom “Back to You” in 2007. It was supposedly set in Pittsburgh, but clearly the writers were unaware that there were linguistic differences between the Mid-Atlantic and Southern California. In a traffic report scene, one of the characters reported that there was congestion on the “freeway”. That’s how a Californian would say it, but exactly not how a Pittsburgher would say it; we’d say “highway” (or “parkway”).
The Psy Guy suggested putting this distinction to SeeTweet, and we see that California is the freeway capital. But Seattle, Miami, and a few Great Lakes cities (Detroit, Cleveland, and Chicago) have substantial “freeway” usages as well. “Highways” are more evenly distributed, with a focus on the Midwest and Mid-Atlantic coast.