Lenght

From reading these forums for many, many years now and having this same similar question asked many times, I have come to a conclusion.

If you are primarily camping anywhere West of the Rockies, a 25 foot travel trailer will accommodate just about anywhere.

If you are primarily camping anywhere East of Kansas, a 35-40 foot travel trailer can be accommodated almost anywhere, provided you check each individual campground first. Most will accomodate trailers of that length and sites available. But not necessarily in thick wooded, jungles.

National Forests everywhere are primarily designed for around 25-30 foot trailers, and there are some exceptions for longer sites, so check ahead first.

Having traveled / camped here in Ontario and many US states from east to west I'd say a good universal length that will get you on pretty well any site is no more than 25' coupler to bumper. This is especially useful when traveling, not reserving but instead just showing up. That said, I never had any site I couldn't fit on to with our previous Spree which measured 26' 9" coupler to bumper BUT there were a few times it was really tight - ergo, why 25' tops to me would be as long as I'd want to go. JMO. ;)

Most campgrounds were first developed in the 1950s and 60s based upon the station wagon and tent camping. Things have changed a bit since then and campgrounds are being redesigned and rebuilt as funds allow. The key phrase is "as funds allow". It's expensive. One popular FS lakefront campground near us was rebuilt to contemporary RV standards at a cost of $1.5 million.
The land agencies are competing with every other agency and program for a limited pool of funds. The campgrounds are being rebuilt to accommodate RVs. It is going to take time to get all of them done.

One thing to keep in mind, near most national and state parks there will be private campgrounds close by. We have a 38 foot 5th wheel and have always been able to find a place to stay within 25 miles or less of the national or state parks we wanted to visit.

Great thing about private parks is you can get full hook ups which can help make the whole experience more enjoyable. It's bad when the batteries die while you are trying to take a shower with no hook ups. That happened to us in our 25 foot TT at Zion National Park in 1980.

Because of posts on here that 36' was the max so I bought a used 36' DP. Did not take long to learn 36 max was BS, especially in the West. Traded for a 40' costing a fair amount and once we could use more than 100 days/year bought current rig slightly used...again costing $$$. Buy more RV than you think you need ONE TIME!!!

We mainly stay in USFS CGs BUT do not show up Friday hoping to find a site big enough. Not sure who determines the max size in CGs as I'm usually able to get in even when it says 30' max.

We went form a 26'tt to a 34'tt. Wished we had stayed smaller and will go back once kids are a bit older. We are much more restricted to where we fit now.

I would try to keep it under 28' and you should have no problems anywhere. Coming from a TC you should find that cavernous in comparison.

Our camper has a 21’ box and we have not had a problem getting into any spot. We go to lots of state parks and some have had few spots for large campers while others have plenty.
I would guess that coming from a TC, anything over 16’ or so would feel large. When we went from a 14’ box to a 23’, it seemed palatial.

We have a 25 foot Dutchmen and have traveled a quite a bit. At Glacier National Park spaces were limited, even PUPs were tough in spots. But in general this is rare.

Out West many of the campsites are smaller but that doesn't stop them from packing rigs in like sardines.

Usually were able to avoid such problems but once or twice we just had to tough it out. Of course we were gone most of the day sight seeing.

In the end you pick the floor plan you like, our floor plan included the ability to wind through city streets and find quilt and gun shops. For us that was 25 to 28 feet.

Rent the size TT you think you like before you buy, you learn a lot real fast.

Good luck

Use spell check on your title.

Try to stay under 30’ overall but you give up a lot for that. If I was going big I would stay under 35’ and get a fifth wheel or a class A.