Register your trailer in Maine!
You do not need to live in Maine, or have a Maine mailing address.
License plate/registration fee is $20 per year, weight does not matter, and you can register for up to 12 years at one time.
There are currently well over 850,000 trailers registered in Maine (the population is only 1.5 M).
Call... Country Wide Trailer Registrations (Jen? I think)
Their phone number is: 207-922-2650
As you drive around, check out over the road trailers, you will see LOTS of Maine trailer plates.