If I were doing this, I would fly to Salt Lake or Denver and rent a car. This would save 4-6 days of really boring driving. If you only have 2 weeks, why spend a quarter of it driving across the Plains?

You didn't tag Arizona or Utah, so maybe you aren't interested in the Southwest. September, though, is a good time to visit National Parks such as the Grand Canyon, Zion, Bryce, Capitol Reef, Monument Valley, etc. You could do a two week trip just visiting them.

Another great 2 week trip would be out of Denver driving through the Rockies and maybe visiting Santa Fe, NM, Mesa Verde, Durango, and possibly Moab, Utah. There's great scenery in Colorado, Northern New Mexico, and Eastern Utah and these are all within a few hundred miles of Denver.

Or, you could go North and visit Yellowstone, Grand Tetons, Glacier and maybe Stanley, Idaho as a loop from Salt Lake City. September is a good time to visit these places too.

I'd skip California and the West Coast. You don't have enough time. Save them for another and separate trip.

I would head straight for the west coast of Washington and Oregon. There is a lot of hiking and nice campgrounds if you are into camping along the way. Mount Rushmore - maybe Yellowstone, Montana, Idaho, great campgrounds on the Pacific Coast of Washington and Oregon.

Depending upon how much time you are in each place you could follow the highway down to San Francisco, go to Yosemite Park and then head back to Chicago.

So many possibilities and whichever route you choose, you will have a wonderful time. The west is absolutely the best.
Idaho alone would offer you hiking, scenery, check out Riggins on the Salmon River and Coeur d'Alene Idaho.

Two days of driving would get you to the Rockies and that is where I would stop. No point of going on to the west coast. Get a good guidebook for Colorado,Wy from your local library and plan it. You have a wide range of low cost options.

I meant to tag Utah, I'm not sure why it didn't come up. I was contemplating flying west first and going from there, so that's definitely something I want to consider doing, rather than take all my time up driving. I would love to camp out, but I'm not sure who will be my travel companions at this point, and if it's just a couple girls I'm not sure how safe we'll feel. Thank you so much for all your suggestions though, I'll definitely have to check out that Colorado guidebook! I'm getting excited just thinking about all the options

Fly to Seattle and in two weeks you can explore the Olympic Peninsula and Vancouver Island as well as the Cascades, Mt. St. Helens, Mt. Hood, Columbia River gorge, even into Idaho and Western Montana such as Glacier Park.
But you could easily spend two weeks just in CO or combine jsut CO with Grand Tetons/Yellowsone in 2 weeks.

Waaaayyy back-in-the-day (like 1981) a friend & I drove from CT to CA & back in 3 weeks. North out, South back. Would I do it again? Probably, just not the same way. I like Super's idea of flying first & renting a car. No disrespect to the midwest, but it IS pretty boring driving.

On our tour we hit (in no particular order, since I can't remember that long ago) Mount Rushmore, Devil's tower, the Badlands, Lake Tahoe, the Grand Tetons, Yellowstone, the Grand Canyon, San Francisco, Monterrey, Disneyland and, of course, Wall Drug (saw signs every few miles & it worked, we just HAD to stop). Lots of other great sights, too.
Unfortunately, the short window left us with very little time at any one spot. It would have been great to linger in some spots. However, I have memories to last a lifetime.

Good luck with your planning, but seriously consider the fly-first option. Enjoy your big adventure.

Hi Duster87....I am also from the Chicagoland area (Northern Indiana) I am now living in the Four Corners area here in the magical Southwest. You mentioned you like to hike. If you decide to visit this area to see Mesa Verde or Monument Valley.....you might want to take look at both of my blogs of my hiking adventures of the ancient Indian (Anasazi) ruin in this area. The first one is called "Beyond Mesa Verde" and has alot of information, including some reviews on guide books. Kelsey's guide is a must if you are traveling the Colorado Plateau. Here is the address for that blog.
http://reddirtdawg.blogspot.com/

The next site is just a blog of my most recent shots of "Rock Art" and other sites in the same area. It is called "Anasazi Ruins"
http://anasaziruins.blogspot.com/

Hope these give you better insight into this wonderful area of the West.

DH and I did this road trip back in '95 I think it was. Two weeks also. Northern route out, Southern route back. It was tight but we covered a lot of ground. Will try to list some of our stops. Started out going up to see the Badlands and Mt. Rushmore. Devil's Tower and Yellowstone. Then into California to visit Yosemite. Stopped at my folks who lived there. Drove up to Monterey while we were there. After that, down to Grand Canyon. Saguara National Park in Arizona. Carlsbad Caverns. And then long boring drive home. But what a trip!

Do remember some hair raising roads too, thank god some of them were driven in the dark. Yikes.

Dusty
Being on a budget, I would not fly and then rent a car. It will be much cheaper to drive. Our national parks are beautiful and you can purchase a yearly pass for $80.00 that will admit you to any of our national parks for a year. http://www.nps.gov/fees_passes.htm Also, their is a little green booklet available at tourist,visiter stations when you cross state lines and it is also available in some gas stations. It is called 'Room Savers' and contains coupons for really good hotel rates in different cities.

It's a LONG and extremely boring drive. I did it just once (when I moved to Seattle). Never again. Not my idea of a good time.