D'oh, how far was that drive from Phoenix to Billings? 
(I see everyone has washed TAR 8 out of their heads...)
Neobie,
Who cares, as it was not one continuous segment. It was broken down into these segments:
Phoenix to Glen Canyon/Lake Powell
Lake Powell to Monument Valley
Monument Valley to Moab UT
Moab UT to Park City UT
Park City to Salt Lake City UT
Park City to Bonneville Salt Flats UT
Bonneville Salt Flats to Yellowstone N.P., Old Faithful Geyser
Yellowstone N.P. to Dubois WY
Dubois WY to Cody WY
Cody WY to Red Lodge Mountain MT
Red Lodge Mountain to Green Meadow Ranch MT
So, the longest segment on this trip is Bonneville Salt Flats to Old Faithful Geyser. The part from Bonneville back to Salt Lake City is about 100 miles depending on precisely where it was. From Salt Lake City to Yellowstone southern entrance is 369 miles. From the southern entrance to Old Faithful is about 30 miles. Add it all up and you get 499 miles. That's certainly enough to put it on this list, but not enough to win the prize.