Both. Jackson Hole is a valley about 80 miles long and 15 miles wide; Jackson is the major town within the valley. The hole begins six miles south of Yellowstone Park and tapers down to the width of the Snake River at Munger Mountain, south of Jackson. The town was named Jackson Hole in 1894 when the post office was established. Many other holes were named in the intermountain west during the 1800's but few were marked on the maps.