Johnson City is a trailer court in the suburbs of Portland, Oregon that also is an incorporated city. In 1970, the residents of the trailer court voted to incorporate as a city. Oregon has changed its laws to make it harder to form microcities, but Johnson City, along with Maywood Park and Rivergrove, Oregon remain as microcities of a few hundred people.
I have visited Johnson City, and it looks like a typical small trailer park, although a bit more prosperous and better kept than most. It also has a small park and small lake. And, along with the property management office, a city hall.
Brevity Quest 2020