Originally Posted by 05CrewDually
Don't live by that info at that link. Check with the portal states your traveling. As long as you're on the Interstate highways in the states in between the portals you will be fine. Also, towing one other trailer behind a 5th wheel (like the pic above) is considered double trailer towing, not triple tow. Triple tow would be 3 trailers.
Semantics...I think it might depend of where you are from or standing at the moment (Camper/trailer/RV or Soda/Pop/Coke)
I've seen it called both but for the purpose of that link, it's refereed to as Triple Tow
this link has a map, and it looks like it's not allowed mostly on the East coast and PNW. and refers to it as Double Tow but doesn't get into much on the details (like some states the one in the middle must be a 5th wheel and max lengths)
State Laws Can Pull You in Many Directions if You Double Tow - PickupTrucks.com News