The Williams Companies, Inc., together with its subsidiaries, operates as an energy infrastructure company primarily in the United States. It operates through Transmission & Gulf of Mexico, Northeast G&P, West, and Gas & NGL Marketing Services segments. The Transmission & Gulf of Mexico segment comprises natural gas pipelines; Transco, Northwest pipeline, MountainWest, and related natural gas storage facilities; and natural gas gathering and processing, and crude oil production handling and transportation assets in the Gulf Coast region. The Northeast G&P segment engages in the midstream gathering, processing, and fractionation activities in the Marcellus Shale region primarily in Pennsylvania and New York, and the Utica Shale region of eastern Ohio. The West segment consists of gas gathering, processing, and treating operations in the Rocky Mountain region of Colorado and Wyoming, the Barnett Shale region of north-central Texas, the Eagle Ford Shale region of South Texas, the Haynesville Shale region of northwest Louisiana, the Mid-Continent region that includes the Anadarko and Permian basins, and the DJ Basin of Colorado; and operates natural gas liquid (NGL) fractionation and storage facilities in central Kansas near Conway. The Gas & NGL Marketing Services segment provides wholesale marketing, trading, storage, and transportation of natural gas for natural gas utilities, municipalities, power generators, and producers; asset management services; and transports and markets NGLs. The company owns and operates 33,000 miles of pipelines. The Williams Companies, Inc. was founded in 1908 and is headquartered in Tulsa, Oklahoma.

Enterprise Products Partners L.P. provides midstream energy services to producers and consumers of natural gas, natural gas liquids (NGLs), crude oil, petrochemicals, and refined products. It operates in four segments: NGL Pipelines & Services, Crude Oil Pipelines & Services, Natural Gas Pipelines & Services, and Petrochemical & Refined Products Services. The NGL Pipelines & Services segment offers natural gas processing and related NGL marketing services. It operates natural gas processing facilities located in Colorado, Louisiana, Mississippi, New Mexico, Texas, and Wyoming; NGL pipelines; NGL fractionation facilities; NGL and related product storage facilities; and NGL marine terminals. The Crude Oil Pipelines & Services segment operates crude oil pipelines; and crude oil storage and marine terminals, which include a fleet of approximately 250 tractor-trailer tank trucks that are used to transport crude oil. It also engages in crude oil marketing activities. The Natural Gas Pipelines & Services segment operates natural gas pipeline systems to gather, treat, and transport natural gas. It leases underground salt dome natural gas storage facilities in Napoleonville, Louisiana; owns an underground salt dome storage cavern in Wharton County, Texas; and markets natural gas. The Petrochemical & Refined Products Services segment operates propylene fractionation facilities, including propylene fractionation units and propane dehydrogenation facilities, and related marketing activities; butane isomerization complex and related deisobutanizer operations; and octane enhancement, isobutane dehydrogenation, and high purity isobutylene production facilities. It also operates refined products pipelines and terminals; and ethylene export terminals; and provides refined products marketing and marine transportation services. Enterprise Products Partners L.P. was founded in 1968 and is headquartered in Houston, Texas.

Energy Transfer LP provides energy-related services. The company owns and operates natural gas transportation pipeline, and natural gas storage facilities in Texas and Oklahoma; and approximately 20,090 miles of interstate natural gas pipeline. It also sells natural gas to electric utilities, independent power plants, local distribution and other marketing companies, and industrial end-users. In addition, the company owns and operates natural gas gathering pipelines, processing plant, and treating and conditioning facilities in Texas, New Mexico, West Virginia, Pennsylvania, Ohio, Oklahoma, Arkansas, Kansas, Montana, North Dakota, Wyoming, and Louisiana; natural gas gathering, oil pipeline, and oil stabilization facilities in South Texas; and transports and supplies water to natural gas producer in Pennsylvania. Further, it owns 5,700 miles of natural gas liquid (NGL) pipeline; NGL fractionation facilities; NGL storage facilities; and other NGL storage assets and terminal. Additionally, the company provides crude oil transportation, terminalling, acquisition, and marketing activities; owns and operates approximately 14,500 miles of crude oil trunk and gathering pipelines in the Southwest, Midcontinent, and Midwest United States; and sells and distributes gasoline, middle distillate, and motor fuels and other petroleum products. It also offers natural gas compression services; carbon dioxide and hydrogen sulfide removal services; and manages coal and natural resources properties, as well as sells standing timber, leases coal-related infrastructure facilities, collects oil and gas royalty, and generate electrical power. The company was formerly known as Energy Transfer Equity, L.P. and changed its name to Energy Transfer LP in October 2018. Energy Transfer LP was founded in 1996 and is headquartered in Dallas, Texas.

Atmos Energy Corporation, together with its subsidiaries, engages in the regulated natural gas distribution, and pipeline and storage businesses in the United States. It operates through two segments, Distribution, and Pipeline and Storage. The Distribution segment is involved in the regulated natural gas distribution and related sales operations in eight states. This segment distributes natural gas to approximately 3.3 million residential, commercial, public authority, and industrial customers; and owned 73,689 miles of underground distribution and transmission mains. The Pipeline and Storage segment engages in the pipeline and storage operations. This segment transports natural gas for third parties and manages five underground storage facilities in Texas; provides ancillary services customary to the pipeline industry, including parking arrangements, lending, and inventory sales; and owned 5,645 miles of gas transmission lines. Atmos Energy Corporation was founded in 1906 and is headquartered in Dallas, Texas.

National Fuel Gas Company operates as a diversified energy company. It operates through four segments: Exploration and Production, Pipeline and Storage, Gathering, and Utility. The Exploration and Production segment explores for, develops, and produces natural gas and oil. The Pipeline and Storage segment provides interstate natural gas transportation services through an integrated gas pipeline system in Pennsylvania and New York; and storage services through its underground natural gas storage fields. This segment also transports and stores natural gas for National Fuel Gas Distribution Corporation, as well as for utilities, industrial companies, and power producers in New York State. The Gathering segment builds, owns, and operates gathering facilities in the Appalachian region, as well as provides gathering services to Seneca. The Utility segment sells natural gas to retail customers; and provides natural gas utility services to various customers in Buffalo, Niagara Falls, and Jamestown, New York, as well as in Erie and Sharon, Pennsylvania. National Fuel Gas Company was incorporated in 1902 and is headquartered in Williamsville, New York.

Black Hills Corporation, through its subsidiaries, operates as an electric and natural gas utility company in the United States. The company operates in two segments: Electric Utilities and Gas Utilities. The Electric Utilities segment generates, transmits, and distributes electricity to approximately 222,000 electric utility customers in Colorado, Montana, South Dakota, and Wyoming; and owns and operates 1,394 megawatts of generation capacity and 9,106 miles of electric transmission and distribution lines. The Gas Utilities segment distributes natural gas to approximately 1,116,000 natural gas utility customers in Arkansas, Colorado, Iowa, Kansas, Nebraska, and Wyoming; owns and operates 4,663 miles of intrastate gas transmission pipelines; 42,514 miles of gas distribution mains and service lines; seven natural gas storage sites; and approximately 50,000 horsepower of compression and 516 miles of gathering lines. It also constructs and maintains customer owned gas infrastructure facilities for gas transportation customers; and provides appliance repair services to residential utility customers, as well as electrical system construction services to large industrial customers. In addition, the company produces electric power through wind, natural gas, and coal-fired generating plants; and coal at its coal mine located near Gillette, Wyoming. Black Hills Corporation was incorporated in 1941 and is headquartered in Rapid City, South Dakota.

Suburban Propane Partners, L.P., through its subsidiaries, engages in the retail marketing and distribution of propane, renewable propane, fuel oil, and refined fuels in the United States. The company operates through four segments: Propane, Fuel Oil and Refined Fuels, Natural Gas and Electricity, and All Other. The Propane segment is involved in the retail distribution of propane for space heating, water heating, cooking, and clothes drying for use as a motor fuel in internal combustion engines to power over-the-road vehicles, forklifts, and stationary engines, as well as to fire furnaces as a cutting gas to the industrial customers; and for tobacco curing, crop drying, poultry brooding, and weed control in the agricultural markets. It also engages in the wholesale distribution of propane to industrial end users. Its Fuel Oil and Refined Fuels segment engages in the retail distribution of fuel oil, diesel, kerosene, and gasoline to residential and commercial customers for use in primarily as a source of heat in homes and buildings. The Natural Gas and Electricity segment markets natural gas and electricity to residential and commercial customers in the deregulated energy markets in New York and Pennsylvania. The All Other segment sells, installs, and services a range of home comfort equipment, including whole-house heating products, air cleaners, humidifiers, and space heaters. The company serves residential, commercial, industrial, and agricultural customers primarily in the east and west coast regions of the United States, as well as portions of the Midwest region of the United States and Alaska. Suburban Propane Partners, L.P. was founded in 1945 and is based in Whippany, New Jersey.

Unitil Corporation, a public utility holding company, engages in the distribution of electricity and natural gas. It operates through two segments, Utility Electric Operations, Utility Gas Operations. The company distributes electricity in the southeastern seacoast and state capital regions of New Hampshire, and the greater Fitchburg area of north central Massachusetts; and distributes natural gas in southeastern New Hampshire and portions of southern and central Maine, including the city of Portland and the Lewiston-Auburn area, as well as electricity and natural gas in the greater Fitchburg area of north central Massachusetts. It also operates 86 miles of interstate underground natural gas transmission pipeline that provides interstate natural gas pipeline access and transportation services primarily in Maine and New Hampshire. In addition, the company provides real estate management services. It serves approximately 108,100 electric customers and 87,500 natural gas customers. Unitil Corporation was incorporated in 1984 and is headquartered in Hampton, New Hampshire.