There is a 63-mile stretch of Interstate 19 outside Tucson, Arizona that is unique for one reason:

It is the only road in the United States which uses the metric system.

Instead of displaying miles from the next exit, the signs are in kilometers. Instead of miles-per-hour for speed limits, the signs show kilometers-per-hour.

You didn’t know that, didja?
Don’t worry, I didn’t either.

Here’s another interesting stat:

Of the 193 countries in the world, every one of them uses the metric system for measurements, except one: the United States.

(This may be worse than that whole “maternity leave” fiasco I wrote about here.)

With the metric system, it seems the US made an attempt but then failed to change. As it turns out, this is a fairly common mistake among leaders. But we’ll get to that in a second.