>>428637>in order of most to least favoriteBig Bend
Yellowstone
Guadalupe Mountains
Rocky Mountain
Grand Tetons
Grand Canyon
Mesa Verde
Carlsbad Caverns
Great Smoky Mountains
Hot Springs
Mammoth Cave
I live near Muleshoe National Wildlife Refuge and get out there a couple times a month on average, even if just for an afternoon. Seeing a few thousand cranes on one small lake in the desert southwest is a great experience and there are three lakes on the refuge. Padre Island National Seashore is nice, too, but it's basically unmolested beach where you can just enjoy the ocean. Who'd want to do that?
The more visited parks like Jellystone, RMNP, Grand Canyon, and GSM are crowded. Plan to hike if you don't like crowds.
Big Bend is where the desert and the mountains make sweet, sweet love. Go in March if you're not from somewhere hot.
Feature parks, like the caverns, Mesa Verde, Hot Springs, and much of Grand Canyon and Yellowstone, will have lots of people at the only things worth seeing. Skip them or go at off times if you don't like crowds.
My wife has MS and we are more limited as far as getting away from the crowds than we used to be, but we still love taking our kids because those parks are the only places to see some of what those parks are there to protect. Sipping a cold beer and holding your wife on the upstairs patio at the Old Faithful Inn (a lovely building, I might add) with somebody playing piano in the background as the geyser goes off and the sun is setting is an experience not to be missed.
If you've been to Carlsbad Caverns, don't bother with Mammoth. You can't see as much of it and the cave is boring. If you've been to Mammoth but haven't been to Carlsbad, get there. You can see much more of the cave, there are several caves you can see, and the features are magnificent.
If you go to Mammoth, rent a canoe and float down the Black River. If you go to GSM, get a ride on a wagon. Your kids will love it. Pic related.