Jim -
Have made that x-c trek many times, and with all due respect to Spencer - I90 has better stuff than I80.
A couple of trip pointers -if you're planning to cross NYS on I90 (the Thruway), there's a much better route now. In Albany, take I88 down to Binghamton and then across thru Jamestown to PA. It's faster, cheaper and more scenic. Continue on I80/90 past Chicago, avoiding driving thru it directly unless you have some burning desire to do, and turn north on I39 in Lasalle. Shortly thereafter, in Rockford, you'll pick up I90.
As you approach Mitchell, SD you'll see signs for the Corn Palace, which as you might expect, is made of corn cobs. It's really hokey, but if you had to live in ND you take your fun where you can get it, so it's worth a drive by at least. Shortly thereafter you'll pass Wall, SD and by that time you will have read hundreds of billboards for Wall Drug, so ... it's worth a stop to see what has to been the world's largest display to totally tasteless and cheap trinketry ever assembled. It's a total bust, but at least you can promise yourself you'll never stop there again unless you get caught in a ice fog in January at -22F (as I did) and in those conditions anything looks good.
Now you'll begin to get within striking distances of lots of National Parks. The first major one is Badlands, and it's worth a drive thru, although it pales in comparison to most of the state of Utah, just to provide some sense of perspective. Outside of Rapid City is Mt Rushmore - worth a stop, although try to view it from the 'old' section (it's downhill from the 'new' section). Don't spend too much time there - rather, plan on spending about 1/2 a day a few miles away at Crazy Horse Monument. Makes the effort at Rushmore look like small potatoes. It's a fascinating place - a work in progress, and totally private, and will be a tribute to that famous Lakota Chief and other native heroes. There's a scenic loop north from Spearfish (Harley Heaven) to Devils Tower (remember Close Encounters of the 3rd Kind?). In Buffalo, WY to south to Riverton and in Lander turn north. There are fabulous views of the Winds on the left for many miles. Make a point of stopping in Fort Washakie at the Indian reservation store (it's on the left) - great authentic stuff. There's a marker for the grave of Sacajawea there, although it's more likely she's buried somewhere along the mouth of the Columbia. From there you're not far from Teton NP and Yellowstone NP (they abut each other). As you leave West Yellowstone, consider taking in the new wolf exhibit - it's on the left as you cross into Idaho. From West Yellowstone, go north along the Gallison River - you'll cross back into WY from time to time. It's got some eye-popping scenery, and if you like shooting rapids, there are lots of companies along this stretch who do trips. From there it's on to Bozeman and Missoula and if you have the time - consider a side trip to Glacier/Waterton NP - it's not too far north of Missoula.
Are you driving back as well? If so, here's a loop to consider - drive east from Portland along the Columbia - many state parks here, and they're simply gorgeous. The goal is to head south, but avoid I5 - boring - so when you reach the Dalles, turn south on US197 and drive down thru Madras and Bend. Many Cascade volcanoes will be on your right as you head south. Stop at Crater Lake, and from there head for Grants Pass. You'll drive along the Rogue River - another wild & scenic river, and stretch your legs on a 20 minute walk along a fascinating chasm at Rogue River SP - it will be on your right as you head south. From Grants Pass continue south on I199 to Cave City. Shortly after crossing into CA you'll be in redwood country, and some of the best are in Jedediah Smith SP. Continue on to Crescent City and then south along US101 thru Redwood NP. In Arcata turn east and follow the West Branch of the Trinity, another wild river famous for rafting and fishing. From Redding continue to Lassen NP - climbing Lassen is great fun, and not a long one, either - maybe 4 or 5 hours if you dawdle. But, it's a real volcano, gets enormous amounts of snow (although not this year) and from its summit you can see its spectular big brother Shasta to the north. From Lassen I'd head to Reno, then across Nevada and visit as many NP's in Utah as time permits - sometimes it seems Utah is just one big national park. It's a beautiful state.
So there you have it - my version of a road trip to from Maine to Oregon. Enjoy the trip with your daughter -
Kevin