Mount Jefferson (Madison County, Montana)

Nomenclature

The nomenclature for Mount Jefferson has seen considerable change and confusion over the years. A.N. Winchell, in his 1914 report, Mining Districts of the Dillon Quadrangle, referred to the highest peak in the Tobacco Roots as "Jefferson Peak, locally called Old Hollowtop." Since that time the more northerly, and higher, of the two adjacent peaks has usually been called Hollowtop. This naming convention is easily explained upon viewing the dish-shaped northeasterly-trending glacial cirque that occupies the top of Hollowtop peak. Information is scanty before 1914. Peale (1896) referred to Ward Peak, near Pony, and “unnamed high peaks” in the range. Present local terminology places Ward Peak further south, near McAlister. The idea that Lewis and Clark named the ranges along with the rivers cannot be confirmed.

Some earlier, published maps labeled the northern peak as Mt. Jefferson. Confusion may arise from the fact that the horizontal triangulation control station (VABM) named JEFFERSON is located on the southern peak, and this designation is found on many maps.

In 1933, Tansley and others referred to the high point of the range as Mt. Jefferson, at 10,600 ft. The northern peak was labeled Mt. Jefferson on the

Reid in 1957 mapped the northern peak as Mt. Jefferson and the southern one as Goat Mountain. In 1960, the Waterloo 15-minute topographic quad showed Mt. Jefferson, to the north, at 10,604’, and the southern one as Hollowtop Mtn (10,513’) with the JEFFERSON control station label. In 1976, the

Oil Company highway maps from the late 1960s and early 1970s show Hollowtop Mtn. at 10,740’, while the Official Montana Highway Map, from at least 1971 onwards, has Hollow Top Mtn. at 10,604’. As recently as 1976, the Beaverhead National Forest map showed Mt. Jefferson to the north (10,604’) and Hollowtop Mtn. with the JEFFERSON control station to the south.

In 1987, the Interagency Visitors Map of Southwest Montana (produced by the Forest Service, USGS, and State of Montana) shows the northern peak labeled Hollowtop Mtn. (10,604’), and the southern peak is marked Mt. Jefferson and includes the control station label. This is the first map known that shows both names, with Hollowtop north of Mt. Jefferson.

Finally, the 1989 7½-minute quad (Noble Peak) also shows Hollowtop Mountain (10,604’) to the north, with Mt. Jefferson (10,513’) to the south with the control station. Numerous hand-held GPS measurements indicate that these listed elevations are probably accurate.

Apparently no peak has an elevation of 10,740’, and all sources agree that the JEFFERSON triangulation station is on the southern peak. Decades of use would have “Hollowtop” to the north, and perhaps the newer maps reflect this usage. The northern peak is labeled “Hollowtop” and “Hollow Top” on various maps, with a single word somewhat more common.

Geology

Most of the mountain is underlain by the Tobacco Root

The bowl-like crest of Hollowtop, best viewed from the towns of

References