Tom,
Not that it makes any difference in this thread, but I keep wondering wonder what references you use for finding altitudes.
Sonora, Texas is at 1825 feet, which is only 5 feet higher than the LOWEST place in Montana, where the Kootenai River flows into Idaho. Even the highest point in Texas, Guadalupe Peak, is only slightly higher than Fort Benton on the Missouri River.
You also once posted that the Prickly Pear shooting range is at 4000 feet, but the Helena airport, down on the valley flats, is at just under 3900 feet, and the range is a noticeable drive uphill into the mountains. The USGS topographic map puts the shooting range's elevation at just about 5300 feet.
