U.S. Border Patrol agents operate an immigration checkpoint Thursday on Interstate 95 in Penobscot County

The government’s crackdown on illegal immigration came to an unexpected place on Wednesday: central Maine – about as far from the border with Mexico as it is possible to get. In Penobscot County, Border Patrol agents set up a vehicle checkpoint for 11 hours, stopping scores of vehicles and arresting a man from Haiti, according to the Portland Press Herald.

We’ve seen other stories of Border Patrol stops in random places in recent months as media attention and the focus of the Trump administration has turned to the subject of immigration. A checkpoint in New Hampshire this week. A woman in Montana was stopped by a Border Patrol agent who heard her speaking Spanish. (She was a citizen, born in Texas.)

There have been a number of stories about Border Patrol agents walking the length of Greyhound buses, asking to see people’s proof of citizenship – enough such stories that Greyhound is now caught up in a political fight largely outside its control.

There is a constitutional protection against being searched without a warrant, raising the question of how such demands from the Border Patrol are legal. If you’re crossing the border, you’re used to having to display a passport. But when you’re in the middle of Maine?

As it turns out, the middle of Maine – and much of northern Montana – are considered to be within the “border zone” of the United States. In fact, the entire states of Maine and New Hampshire are within the border zone, which extends 100 miles into the United States from every border and every coast. According to the American Civil Liberties Union, two-thirds of Americans live within the border zone, a function of the number of major cities located near the coast.

Everyone in New York City lives in the border zone and can be asked to show identification to Border Patrol agents. Everyone in Los Angeles. Everyone in Seattle, Houston, Chicago and the District. Every single person in Florida. An extensive look at the border zone by CityLab determined that more than 7 in 10 nonwhite Americans live in the border zone.

Curious if you’re in the border zone? The Washington Post made a tool that can tell you and you can link to it by clicking to their story here. Using data from the Census Bureau defining the country’s border, the tool below will geolocate you – you have to click a button to allow access – and then tell you about how far you are from the border. Bear in mind that there is naturally a degree of uncertainty to the calculation, given the imprecise nature of the calculations, the geolocation and the resolution of the boundary map.

Nonetheless, it should give you a sense of where the boundary lies.

Most of you will find that you’re in the border zone. Authorities can set a smaller boundary; our tool doesn’t reflect places where that might be the case.

It’s worth noting that while the Border Patrol can operate checkpoints, it cannot simply search your car (for example) without a warrant. Within 25 miles of the border, though, the Border Patrol has even broader powers, including the right to enter private property (except houses) without a warrant.

The ACLU of Arizona has a comprehensive breakdown of your rights when approached by the Border Patrol. We can’t guarantee that showing a Border Patrol agent the results of our tool while he’s demanding you turn over identification will work out all that well for you; the ACLU document notes that “if you don’t answer questions to establish your citizenship, officials may deny you entry to the U.S. or detain you for search and/or questioning.”

But if you’re in the middle of Kansas, and our tool makes clear that you’re more than 600 miles from the nearest border, feel free to point that out.