JOSM - Switch from Metric?

The measurement scale on the upper left is in metric. I’m working on a custom map of America, and I need miles for exit numbers. Is there any way I can switch to the American system?

Go to Edit menu, then Preferences (or press F12).
Click on the third icon down the side of the preferences window.
Then there’s an option for System of measurement, you can set that to Metric / Imperial etc.