An ESRI TIN data set is available for the colored parts of each of the rectangular areas shown on the map below. Click on a rectangle to download the data for that area. Each file is about 100 to 200 megabytes in size. All of the data are in Montana State Plane Coordinates, NAD83, units meters.

This data is also available in USGS DEM format at http://nris.mt.gov/yellowstone/loweryel/2004_dem_yellowstone_west.html
and in ESRI Generate format at http://nris.mt.gov/yellowstone/loweryel/2004_gen_yellowstone_west.html.