James,

I'm not sure if this was 'the big fire' or not although it was pretty big. Total acreage lost in the East Fire was in excess of 18,000 acres. See this topo map:
2003 - Yellowstone National Park - East Fire

It was kind of eerie being there as you could still see smoke rising in areas that you could walk in. There were still plenty of fire fighters along the road. It was not uncommon to see a helicopter carrying a water bucket flying to Lake Yellowstone and returning into this area although we never saw an actual water dump.

Another strange thing that I had noticed from this vantage point was a clear delineation within the forest of trees between burnt and unburnt land almost as if the fire progressed to a certain point and just stopped - black on one side and green on the other.