Thank you so much for the helpful information given so far! I actually had no idea that Trip Advisor had forums for each state. That is excellent! I took a quick peak and it looks like the info will be helpful to sift through. I'll also take a look at the other suggestions given.
I should have clarified in my original post - I'm not planning this trip for this summer... it would be for summer 2021. I'm a teacher and have 3 children, so it will have to be a summer trip. :) I just don't think I'll be comfortable yet getting on a flight to Europe next year, so I'm currently thinking 4-5 week road trip from Chicago, seeing some sights through New Mexico, Arizona, California, and a few parks we haven't hit in Utah yet....
Any advice is welcome! Parks we have already seen out west include: Yellowstone, Grand Teton Nat'l Park, Badlands, Black Hills area, Rocky Mountain Nat'l Park, Black Canyon of Gunnison, Great Sand Dunes Nat'l Park, Arches, Canyonlands, Saguaro, and Muir Woods.
Some sites to hopefully see on this trip would include: Grand Canyon and a few of the smaller parks/monuments in AZ, Sedona (one of my favorite places!), Joshua Tree, San Diego, big national parks in CA :), drive up Route 1/Carmel/Monteray, Bryce Canyon, Zion, and Capitol Reef. I'm sure all of these sites could take a lifetime, but it will be fun to take the year to plan. :)