I asked about this in Maryland as I knew my hitched length was going to be in the 60-65' range. Turns out I'm 59 1/2' long bumper to bumper.
Most of the time, the guides that compile all of the states data don't cover the caveats of the states. For instance, Maryland is often quoted at 55'. Which is right, BUT you can be up to 65' in length as long as you follow a couple of rules.
Here's a snippet of an email exchange:
Maryland State Highway Administration wrote:
Noncommercial power unit and travel trailer combination may be up to 65 feet BUT anything over 55 feet is required to be on specific routes:
1. Interstate system
2. State routes considered authorized "truck routes"
3. Shortest practical route between designated highways and:
a. point of origin and destination on a particular day.
b. for a distance not to exceed 1 mile, facilities for food, fuel, repairs or rest.
Transportation article 24.104.1.m