At last count, around 15 states require a special license for motorhomes over a certain weight.
https://offgridspot.com/do-i-need-a-special-license-to-drive-a-motorhome/
Arkansas - A CDL is required if your RV has a GVWR above 26,000lbs.
Connecticut, Hawaii, Kansas, New Mexico, Washington DC - If it is a single motorhome above 26,000lbs, a class B license is required. Apply for a Class A license if you are towing, and the combined GVWR is above 26,000lbs.
These states require a special non-commercial drivers license:
California - you need a Class B license if the motorhome exceeds 40 feet or 26,000 lbs. If you are towing a trailer above 10,000lbs, a Class A license is required.
Maryland - Class B license is required.
Michigan - special double “R” endorsement, only needed if you tow a trailer and a fifth wheel together (very rare case)
North Carolina - same as California, minus the 40 feet limit.
Nevada - Class B for single motorhome, Class A for multiple (towed) RVs with a combined weight above 26,000lbs, “J” endorsement if multiple towed vehicles are under 26,000 lbs and the towed vehicle is above 10,000lbs.
New York - “R” endorsement for all RVs above 26,000lbs.
Pennsylvania - Class B license, same as California
South Carolina - Class E license for single motorhome, Class F for multiple RV-trailer combos above 26,000 lbs combined weight.
Texas - Same as California, minus the 40 feet requirement
Wyoming - Class B license for motorhomes with or without towed vehicles under 10,000lbs, Class A if the towed vehicle is above 10,000lbs (combined weight is above 36,000lbs).