Coordinates: 40°46′N 111°53′W / 40.767°N 111.883°W / 40.767; -111.883

Questar Corporation is a natural gas-focused energy company based in Salt Lake City, Utah in the Rocky Mountains. Questar's three major lines of business — retail gas distribution, interstate gas transportation and gas production — are conducted through its principal subsidiaries: Questar Gas, Questar Pipeline and Wexpro. Wexpro is an oil and natural gas producer in the Rocky Mountains.

Previously known as Mountain Fuel Supply Company the company reorganized under a holding company in 1984 and is publicly traded as Questar Corporation. Mountain Fuel Supply formally changed its name to Questar Gas Company in 1998.

Questar Corporation's origins began in 1928, as a holding company named Western Public Service Corporation. That company was formed to bring natural gas to the Salt Lake City region of northern Utah from fields across the state border to the east in southwestern Wyoming. Mountain Fuel Supply Company was at that time the name of the holding company's oil and gas exploration and production affiliate.

In 1935, the shareholders voted to reorganize Western Public Service Corporation as a single company. Mountain Fuel Supply Company (MFS) then became the name of the reorganized consolidated company, which was publicly traded on the New York Stock Exchange under that name from then until 1984. Beginning in 1935, it also paid a cash dividend to shareholders every year since that time.

In 1963, the company began to use a new trademark logo, in the shape of a trapezoid. That logo remained in use until becoming Questar Gas in 1998.

In 1984, Mountain Fuel Supply Company shareholders voted to return to the holding-company structure, and chose the name Questar Corporation as the new parent holding company name. Questar Corporation continues to trade on the NYSE, under its stock symbol STR.

Construction began in August 2010 on a new $45 million 6-story building at 333 South State Street in downtown Salt Lake City, Utah. The new facility was completed and opened in March 2012. The 170,000-square-foot (16,000 m) building replaces Questar's former headquarters located at 180 East 100 South. The new Questar Center building is one of the first LEED Silver energy-efficient buildings in downtown Salt Lake. The new headquarters accommodates some 600 Questar employees in a floor plan that is 20 percent smaller than Questar's former headquarters. Employees working at Questar's D.N. Rose operation center in Salt Lake City will continue to operate from that location as well.

On January 1, 1998, Mountain Fuel Supply Company was renamed Questar Gas Company, bringing all of Questar's divisions under the single Questar brand name. The move was prompted by new deregulation in the energy industry, which allowed the company to offer wider choices to customers, and to venture into new lines of business. The old Mountain Fuel Supply name had been primarily associated with natural gas delivery up until that time. In 1998 the Questar Corporation also began to use its newly reworked version of the traditional trapezoid logo throughout the organization.

At the time, R. D. Cash was chairman, president and chief executive officer of Questar Corporation.

Other Questar affiliates were already moving into newly available energy market areas, such as Questar Energy Trading, which had begun to market electricity on the wholesale level, and Questar Energy Services, which had begun selling retail products including earthquake braces and carbon-monoxide monitors, and providing home-security and appliance-maintenance services. Also, Questar InfoComm began selling information technology and telecommunications.

By 1998, Questar Corporation had become one of the largest companies headquartered in Utah, with 2,500 employees and about US$1.8 billion in assets. The company had two major divisions:

In April 2003, D. N. "Nick" Rose, president and chief executive officer of Questar Regulated Services, retired and Alan K. Allred, who served as executive vice president and chief operating officer of the QRS group, succeed Rose.

By 2006, the Regulated Services segment had been subdivided instead into segments named Questar Gas and Questar Pipeline, for a total of three primary subsiary companies within Questar, with four major lines of business:

In 2005, Knox Lawrence International acquired Consonus Inc., a Questar subsidiary which was formed 5 years ago and had housed and managed computer data centers for dozens of businesses. Questar Corp. was getting out of the data center management business.

On July 1, 2010, Questar Market Resources (QMR) exploration and production business was spun off to form a new publicly traded company, QEP Resources, Inc. (NYSE: QEP). QEP established its company headquarters in Denver, Colo. Questar Corporation's board of directors elected Ron W. Jibson as president and CEO.

On October 19, 2014 Tesoro Logistics LP agreed to buy QEP Resources Inc.’s natural-gas pipeline and processing business for $2.5 billion in cash to expand its business in the Rocky Mountains and North Dakota.

It was announced on February 1, 2016 that Dominion Resources, an energy company based in Richmond, Virginia, would be purchasing Questar Corporation for $25 dollars a share (about $4.4 billion).

On September 16, 2016 the Dominion Resources and Questar Corporation merger was officially completed. Dominion Questar becomes the official name for the Salt Lake City based subsidiary of Dominion Resources. Current CEO of Questar Corporation, Ron Jibson, is named to the board of directors at Dominion Resources following the completion of the merger.

Questar's operations consist of three major lines of business — retail gas distribution, interstate gas transportation and gas production.

Questar Gas Company (QGC) — retail gas distribution — is a public natural gas utility in Utah, southwestern Wyoming and southeastern Idaho.

Questar Pipeline Company (QPC) — interstate pipeline and storage in Utah, Wyoming and Colorado.

Wexpro Company (WEX) — develops and produces gas and oil on certain properties for affiliate Questar Gas under the terms of a long-standing comprehensive agreement with the states of Utah and Wyoming. Wexpro delivers natural gas production to Questar Gas at a price equal to Wexpro's cost of service.