Really good maps and its made of some sort of paper that is kind of water proof.
I traveled all over the US after high school and before smartphones. For traveling, you want very detailed roads. I used an atlas. One map of the US can’t be as detailed as you want it. To use individual state folding maps is kind of cumbersome. The best option is an atlas. Now a days, they are fantastic back ups if the smartphone doesn’t work. Good thing to have in general. I love National Geographic maps. I’d probably get this one https://www.amazon.com/National-Geographic-Road-Atlas-Adventure/dp/0792289897.
With 10 people in the group what do you plan to drive? Have you reserved it/them? Buy one of these. It will help you plan your stops and route. You can all consult it to determine the next day's itinerary. https://www.amazon.com/National-Geographic-Road-Atlas-Adventure/dp/0792289897/ref=sr_1_1?crid=2OBX6YYRD0UKQ&dchild=1&keywords=national+geographic+road+atlas&qid=1618957339&sprefix=National+geographic+roa%2Caps%2C256&sr=8-1
I follow your friend on IG! Get her this: National Geographic Road Atlas 2021: Adventure Edition [United States, Canada, Mexico] https://www.amazon.com/dp/0792289897/ref=cm_sw_r_cp_api_i_Y6wxFb09RD1BJ
If you're in the US, the atlas to get is the National Geographic Adventure Edition. I carry Delorme atlases for a few states as well.
I'd get an Atlas and a National Parks pass. Each state will have its own page(s) in the atlas and you can plan your route and stops before you start or each day as you drive.