Just for fun...
I went thru all 58 National Parks NPS Site and looked for length restrictions....I have listed the Maximum Restriction I could find for that park. Some campsites obviously may not have sites that long, but somewhere in the park, they limit you to the listed length.
"NL" meand I couldn't find a restriction (there may not even be a Campground there!)
I gave it my best shot but started getting really bored by the time I got to 'Nevada'...
Alaska National Parks
Denali National Park, "A" sites can accommodate tents and RV's 30-40' (max) in length
Gates of the Arctic National Park, located above the Arctic Circle and far from any roads
Glacier Bay National Park NL
Katmai National Park, there is no road access
Kenai Fjords National Park NL
Kobuk Valley National Park NL
Lake Clark National Park NL
Wrangell-St. Elias National Park NL
Arizona National Parks
Grand Canyon National Park ...These will hold up to a 34-ft. fifth-wheel
Petrified Forest National Park NL
Saguaro National Park NL
Arkansas National Parks
Hot Springs National Park 30 and 50 amp electrical connections…No length mentioned
California National Parks
Channel Islands National Park NL
Death Valley National Park NL
Joshua Tree National Park 8 campgrounds, 2 with length restrictions
Kings Canyon National Park 14 campgrounds, some list No Trailers. All others have no listed limits
Lassen Volcanic Park NL
Redwood National Park Vehicle Length Limit: 36-foot RV or 31-foot trailer.
Sequoia National Park RVs can also stay in parking lot.
Yosemite National Park maximum trailer length is 35 feet
Colorado National Parks
Black Canyon of the Gunnison National Park Vehicles greater than 35 feet are not recommended
Great Sand Dunes National Park can accommodate RVs or camping trailers up to 35 feet in length
Mesa Verde National Park NL
Rocky Mountain National Park Moraine Park-40 ft motor homes & trailers
Florida National Parks
Biscayne National Park NL
Dry Tortugas National Park NL
Everglades National Park NL
Hawaii National Parks
Haleakala National Park NL
Hawaii Volcanoes National Park NL
Kentucky National Parks
Mammoth Cave Park 1 CG listed as Not Suitable for Large Trailers, others NL
Maine National Parks
Acadia National Park sites accommodate pop-ups, vehicle campers, and RVs up to 35 feet
Michigan National Parks
Isle Royale National Park NL
Minnesota National Parks
Voyageurs National Park NL
Montana National Parks
Glacier National Park NL
Nevada National Parks
Great Basin National Park 1 of 4 listed as max 24', other 3, NL
New Mexico National Parks
Carlsbad Caverns National Park NL
North Carolina National Parks
Great Smoky Mountains National Park Max Trailers-35'
North Dakota National Parks
Theodore Roosevelt National Park NL
Ohio National Parks
Cuyahoga Valley National Park NL
Oregon National Parks
Crater Lake National Park NL
Virginia National Parks
Shenandoah National Park Got Tired of digging
South Carolina National Parks
Congaree National Park NL
South Dakota National Parks
Badlands National Park NL
Wind Cave National Park there are no length limits for RVs
Texas National Parks
Big Bend National Park 1 of 3 list max recommended of 20', others NL
Guadalupe Mountains National Park
Utah National Parks
Arches National Park Some sites will accommodate RVs up to 30 feet in length
Bryce Canyon National Park NL
Canyonlands National Park Maximum RV length is 28 feet
Capitol Reef National Park NL
Zion National Park NL
Washington National Parks
Mount Rainier National Park Max Trailer: 27 ft.
North Cascades National Park Large RVs can be accommodated
Olympic National Park RV length (some for up to 35').
Wyoming National Parks
Grand Teton National Park Large RVs can be accommodated
Yellowstone National Park Large RVs can be accommodated
US Territories National Parks
American Samoa National Park NL
Virgin Islands National Park NL