Targa Resources Corp., together with its subsidiary, Targa Resources Partners LP, owns, operates, acquires, and develops a portfolio of complementary domestic midstream infrastructure assets in North America. It operates in two segments, Gathering and Processing, and Logistics and Transportation. The company is involved in gathering, compressing, treating, processing, transporting, and selling natural gas; storing, fractionating, treating, transporting, and selling natural gas liquids (NGL) and NGL products, including services to liquefied petroleum gas exporters; and gathering, storing, terminaling, purchasing, and selling crude oil. It is also involved in the purchase and resale of NGL products; and sale of propane, as well as provision of related logistics services to multi-state retailers, independent retailers, and other end-users. In addition, the company offers NGL balancing services; and transportation services to refineries and petrochemical companies in the Gulf Coast area, as well as purchases, markets, and resells natural gas. As of December 31, 2023, it leased and managed approximately 605 railcars; 137 tractors; and 6 vacuum trucks and 2 pressurized NGL barges. Targa Resources Corp. was incorporated in 2005 and is headquartered in Houston, Texas.

Western Midstream Partners, LP, together with its subsidiaries, operates as a midstream energy company primarily in the United States. It is involved in gathering, compressing, treating, processing, and transporting natural gas; gathering, stabilizing, and transporting condensate, natural gas liquids (NGLs), and crude oil; and gathering and disposing produced water. The company also buys and sells natural gas, NGLs, and condensate. It operates assets located in Texas, New Mexico, the Rocky Mountains, and North-central Pennsylvania. Western Midstream Holdings, LLC operates as the general partner of the company. The company was formerly known as Western Gas Equity Partners, LP and changed its name to Western Midstream Partners, LP in February 2019. Western Midstream Partners, LP was incorporated in 2007 and is based in The Woodlands, Texas.

Plains GP Holdings, L.P., through its subsidiary, Plains All American Pipeline, L.P., owns and operates midstream infrastructure systems in the United States and Canada. It operates in two segments, Crude Oil and Natural Gas Liquids (NGLs). The company engages in the gathering and transporting crude oil and NGLs using pipelines, gathering systems, and trucks. It engages in the loading and unloading services at terminals; NGL fractionation and isomerization services; and natural gas and condensate processing services. The company offers logistics services to producers, refiners, and other customers. PAA GP Holdings LLC operates as a general partner of the company. Plains GP Holdings, L.P. was incorporated in 2013 and is headquartered in Houston, Texas.

Alliance Resource Partners, L.P., a diversified natural resource company, produces and markets coal primarily to utilities and industrial users in the United States. The company operates through four segments: Illinois Basin Coal Operations, Appalachia Coal Operations, Oil & Gas Royalties, and Coal Royalties. It produces a range of thermal and metallurgical coal with sulfur and heat contents. The company operates seven underground mining complexes in Illinois, Indiana, Kentucky, Maryland, Pennsylvania, and West Virginia. In addition, it owns and leases oil and gas mineral interests and equity interests; and leases its coal mineral reserves and resources to its mining complexes; and leases land and operates a coal loading terminal on the Ohio River at Mt. Vernon, Indiana. Further, the company offers various mining technology products and services, including data network, communication and tracking systems, mining proximity detection systems, industrial collision avoidance systems, and data and analytics software. It also exports its products. The company was founded in 1971 and is headquartered in Tulsa, Oklahoma.

Black Stone Minerals, L.P., together with its subsidiaries, owns and manages oil and natural gas mineral interests. It owns mineral interests in approximately 16.8 million gross acres, nonparticipating royalty interests in 1.8 million gross acres, and overriding royalty interests in 1.6 million gross acres located in 41 states in the United States. The company was founded in 1876 and is based in Houston, Texas.

Kimbell Royalty Partners, LP, together with its subsidiaries, engages in acquiring and owning mineral and royalty interests in oil and natural gas properties in the United States. It serves as the general partner of the company. The company was incorporated in 2015 and is based in Fort Worth, Texas.

NACCO Industries, Inc., together with its subsidiaries, engages in the natural resources business. The company operates through three segments: Coal Mining, North American Mining, and Minerals Management. The Coal Mining segment operates surface coal mines under long-term contracts with power generation companies. Coal is surface mined in North Dakota and Mississippi. The North American Mining segment provides value-added contract mining and other services for producers of aggregates, activated carbon, lithium, and other industrial minerals; and contract mining services for independently owned mines and quarries in Florida, Texas, Arkansas, Virginia, and Nebraska. This segment also offers mining design and consulting services. The Minerals Management segment is involved in the leasing of its royalty and mineral interests to third-party exploration and production companies, and other mining companies, which grants them the rights to explore, develop, mine, produce, market, and sell gas, oil, and coal. NACCO Industries, Inc. was founded in 1913 and is headquartered in Cleveland, Ohio.

Summit Midstream Partners, LP focuses on owning, developing, and operating midstream energy infrastructure assets primarily shale formations in the continental United States. The company provides natural gas gathering, compression, treating, and processing services, as well as crude oil and produced water gathering and freshwater delivery services. Its assets include Summit Utica system comprising the Utica and Point Pleasant shale formations in southeastern Ohio; Mountaineer Midstream system that includes the Marcellus shale in the Appalachian Basin in West Virginia; Polar and Divide system includes the Bakken and Three Forks shale formations in northwestern North Dakota; Niobrara G&P system, which comprises the Niobrara and Codell shale formations located near Hereford, Colorado. The company's assets also include Double E, a 135 mile interstate natural gas transmission pipeline; Grand River system that gathers natural gas produced from the Mancos and Niobrara shale formations in western Colorado; and DFW Midstream system comprising the Barnett Shale formation located in north-central Texas. In addition, it owns an ownership interest in Ohio Gathering, which owns and operates natural gas gathering and condensate stabilization facility in the Utica Shale in southeastern Ohio. It serves natural gas and crude oil producers. Summit Midstream GP, LLC operates as a general partner of the company. Summit Midstream Partners, LP was founded in 2009 and is based in Houston, Texas.