Short Hill Mountain is a

mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher ...

ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...

of the

Blue Ridge Mountains The Blue Ridge Mountains are a physiographic province of the larger Appalachian Mountains range. The mountain range is located in the Eastern United States, and extends 550 miles southwest from southern Pennsylvania through Maryland, West Virg ...

in northwest Loudoun County,

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth are ...

Geography

Short Hill rises sharply from the

Piedmont it, Piemontese , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = , demographics1_footnotes = , demographics1_title1 = , demographics1_info1 = , demographics1_title2 ...

countryside of the Loudoun Valley, northwest of

Purcellville Purcellville is a town in Loudoun County, Virginia. The population was 8,929 according to the 2020 Census. Purcellville is the major population center for Western Loudoun and the Loudoun Valley. Many of the older structures remaining in Purcellvi ...

. It is a low-lying ridge, barely over in elevation. The mountain ridge extends northeast for approximately before descending to the

Hillsboro Gap Hillsboro Gap, also known as the Gap in the Short Hill is a water gap in the Short Hill Mountain formed by the North Fork of the Catoctin Creek in Loudoun County, Virginia. The gap derives its name from the town of Hillsboro, which is nestled i ...

, through which the North Fork of Catoctin Creek flows and the town of Hillsboro is located. North of the gap, the ridge quickly achieves heights of greater than , and continues for , gradually gaining elevation, before dropping precipitously to the

Potomac River The Potomac River () drains the Mid-Atlantic United States, flowing from the Potomac Highlands into Chesapeake Bay. It is long,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map. Retrieved Augu ...

. The portion of the mountain south of Hillsboro Gap is known as Signal Mountain for the

Union Army During the American Civil War, the Union Army, also known as the Federal Army and the Northern Army, referring to the United States Army, was the land force that fought to preserve the Union (American Civil War), Union of the collective U.S. st ...

signaling station located on its summit during the

American Civil War The American Civil War (April 12, 1861 – May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States. It was fought between the Union (American Civil War), Union ("the North") and t ...

. North of the Potomac, the ridge continues as

South Mountain South Mountain or South Mountains may refer to: Canada * South Mountain, a village in North Dundas, Ontario * South Mountain (Nova Scotia), a mountain range * South Mountain (band), a Canadian country music group United States Landforms * Sout ...

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean t ...

and

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

. Short Hill is about east of the crest of the

Blue Ridge Mountain Blue Ridge Mountain, also known as Blue Mountain, is the colloquial name of the westernmost ridge of the Blue Ridge Mountains in northern Virginia and the Eastern Panhandle of West Virginia. The Appalachian Trail traverses the entire length of th ...

, which forms the western border of Loudoun County, and the valley in between the mountains is known as

Between the Hills Between the Hills is a small valley in northwest Loudoun County, Virginia, distinct from, but associated with, the greater Loudoun Valley. Geography The Between the Hills valley encompasses the area of Loudoun that lies west of Short Hill Mount ...

and includes the villages of Loudoun Heights and Neersville. To the east of the mountain is the

Catoctin Valley The Catoctin Valley is a small valley, geographically and culturally associated with the larger Loudoun Valley in Loudoun County, Virginia. Geography The Catoctin Valley encompasses the northern part of the Loudoun Valley east of the Short Hi ...

. A small portion of Short Hill on its northwestern slope, along the Potomac, is owned by the

National Park Service The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational properti ...

to preserve downriver views for

Harpers Ferry National Historical Park Harpers Ferry National Historical Park, originally Harpers Ferry National Monument, is located at the confluence of the Potomac and Shenandoah rivers in and around Harpers Ferry, West Virginia. The park includes the historic center of Harpers F ...

. The rest of the mountain is in private hands and is by and large undeveloped. The only road crossing of the mountain is

Virginia State Route 9 Virginia State Route 9 (SR 9) is a primary state highway in the U.S. state of Virginia. Known as Charles Town Pike, the state highway runs from the West Virginia state line near Mechanicsville, where the highway continues west as West Virgini ...

at Hillsboro.

Geology

The rocks underlying Short Hill are of the late

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided i ...

and early

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ...

eras. The formation consists primarily of metabasalt greenstone deposited during the early

Catoctin Formation The Catoctin Formation is a geologic formation that expands through Virginia, Maryland, and Pennsylvania. It dates back to the Precambrian and is closely associated with the Harpers Formation, Weverton Formation, and the Loudoun Formation. Th ...

and interspersed with

metasedimentary In geology, metasedimentary rock is a type of metamorphic rock. Such a rock was first formed through the deposition and solidification of sediment Sediment is a naturally occurring material that is broken down by processes of weathering and e ...

phyllite Phyllite ( ) is a type of foliated metamorphic rock created from slate that is further metamorphosed so that very fine grained white mica achieves a preferred orientation.Stephen Marshak ''Essentials of Geology'', 3rd ed. It is primarily compo ...

schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...

and

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...

, which were deposited later. The rocks were originally deposited contiguous with those of the Blue Ridge Mountains and uplifted together during the

Grenville Orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, f ...

. The two ridges were later separated in the late Paleozoic era by movement along the Short Hill Fault, which runs along the western edge of the mountain. During the

Alleghenian Orogeny The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 195 ...

the rocks were pushed westward to their present location and uplifted once more.

Project Office

Short Hill Mountain north of Hillsboro is home to one of several AT&T Corporation Project Offices, underground facilities constructed in the 1960s to provide redundant communications services. The Short Hill facility was renovated in the late 2010s and remains active.

References

{{Mountains of Virginia Mountain ranges of Virginia Landforms of Loudoun County, Virginia Ridges of Virginia South Mountain Range (Maryland−Pennsylvania)