Tom Dick and Harry Mountain is a two-mile-long volcanic

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 mountain in Clackamas County

Clackamas County, Oregon

Clackamas County is a county located in the U.S. state of Oregon. The county was named after the Native Americans living in the area, the Clackamas Indians, who were part of the Chinookan people. As of 2010, the population was 375,992...

 in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

.
It is located 7.2 miles (11.6 km) southwest of Mount Hood

Mount Hood

Mount Hood, called Wy'east by the Multnomah tribe, is a stratovolcano in the Cascade Volcanic Arc of northern Oregon. It was formed by a subduction zone and rests in the Pacific Northwest region of the United States...

, 1.9 miles (3.1 km) west-southwest of Government Camp

Government Camp, Oregon

Government Camp is an unincorporated community located in Clackamas County, Oregon, United States, south of Mount Hood and north of Tom, Dick and Harry Mountain. It is a gateway to several ski resorts, the most popular being Timberline Lodge and Mount Hood Skibowl. Also, Government Camp has its...

 between the Zigzag River

Zigzag River

The Zigzag River is a tributary, about long, of the Sandy River in the U.S. state of Oregon. The Zigzag and one of its major tributaries, the Little Zigzag River, drain the Zigzag Glacier on Mount Hood, a high volcanic peak in the Cascade Range. Their waters flow westward to meet the Sandy River...

 and Still Creek, south of Zigzag Mountain

Zigzag Mountain

Zigzag Mountain is a volcanic mountain in Clackamas County in the U.S. state of Oregon.It is located west-southwest of Mount Hood, northwest of Government Camp, east of Zigzag, and north of the Zigzag River. Because of its proximity to Mount Hood, it is considered a foothill.The highest peak is ...

. Because of its proximity to Mount Hood, it is considered a foothill.

The mountain is named for its three distinct peaks along the summit, forming the cirque

Cirque

Cirque may refer to:* Cirque, a geological formation* Makhtesh, an erosional landform found in the Negev desert of Israel and Sinai of Egypt*Cirque , an album by Biosphere* Cirque Corporation, a company that makes touchpads...

 that is now part of the Mount Hood Skibowl

Mount Hood Skibowl

Mount Hood Skibowl is a recreation area on Mount Hood located near Government Camp, Oregon. It is the largest night ski area in the United States, and the total skiable area encompasses an area of . The resort is the closest ski venue to Portland, with an elevation of at the lodge, rising to...

 ski resort.
The highest peak is 5066 feet (1,544 m) above sea level. The name was in use as early as 1897, according to Elijah "Lige" Coalman, the namesake of Coalman Glacier

Coalman Glacier

The Coalman Glacier is a glacier located on the upper slopes of Mount Hood in the U.S. state of Oregon. It is the mountain's highest glacier ranging from about 10,500 to 11,200 ft , located within the crater rim, southwest of the peak...

. The mountain has also been called "Tom Dick Mountain" in the past, although the Board on Geographic Names

United States Board on Geographic Names

The United States Board on Geographic Names is a United States federal body whose purpose is to establish and maintain uniform usage of geographic names throughout the U.S. government.-Overview:...

 officially decided in favor of including "Harry" in 1969.

Mirror Lake

Mirror Lake (Mount Hood, Oregon)

Mirror Lake is a mountain lake in Clackamas County of the U.S. state of Oregon. It is located at the foot of Tom Dick and Harry Mountain in a natural catchment formed by a toe of the mountain, southwest of Mount Hood, and WSW of Government Camp within Mount Hood National Forest.It is among the...

, a popular hiking destination, is located on the north side of the mountain.

Both Tom Dick and Harry Mountain and Zigzag Mountain are capped by Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

 andesite

Andesite

Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...

 and basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

.