Your correspondent traveled the East Coast of the USA on a recent day. From nearly the northern reach of civilization, to well south of its southern reach.
In Philadelphia (Pennsylvania), an electric unicycle was sighted sailing around the bend from Market Street where it meets that hideous edifice in the square. In Wilmington (Delaware), no sightings; however, it was noted that the Riverwalk Trail prohibits just about anything that's round, so we must record it as inconclusive. In Baltimore (Maryland), no sightings on Charles Street. In Washington (District of Columbia), a wheel was sighted as it was being walked indoors.
And the point is...? Well, a small sample, strictly time-constrained, without advance notice, naturally the proceeds were humble. I am delighted to have achieved two sightings in distinct cities on the same day. Delighted. All the same, Baltimore is such a cratered, quirky, steeply-inclined place, a place that positively begs for unicycles... most likely, the people I saw on tinny two-wheeled scooters had left their unicycle at home and therefore had to rent something inferior from Bang or Poop or whatever the companies are in that area. If the rental agencies set out unicycles, I'm sure the picture would be quite different.