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Where do highway mileage signs measure to, exactly?

Those mileage marker signs on the side of the road are a great away of letting you know how far you’ve got to go until your destination. But what exactly do they mean? If it says “Denver, 25 miles,” is it 25 miles until the first exit for Denver, or the city center of Denver, or the city limits of Denver, or what? Before you start planning your big summer road trips, here’s a little bit of info you can tell the kids in the backseat when they’re getting restless and want to know how much car time is left.

It’s actually none of the above (or not necessarily). The Federal Highway Administration establishes a “center point” at those sign listed towns and cities, also known as “control cities.” (What makes a control city? It has to have a post office, at the very least). Working the FHA, state laws or local municipalities that have jurisdiction over the roads establish those center points.

The criteria for a center point: It’s nothing set in stone, other than what the FHA calls a “well-defined central area.” That could be a downtown, a central business district, or the central government buildings area. It’s a myth that the signs measure to city hall across the board, although some cities do use that designation, most notably Baltimore. For New York City, the distance is to the busy Columbus Circle.