Who owns MountainWest?
MountainWest is owned by Williams (the United States, NYSE: WMB).[1]
Evidence: The Williams Companies, Inc. Annual Report on Form 10-K filed 2026-02-24, SEC EDGAR, 24 February 2026. Verified from filings; last checked .
Key facts
- Current owner
- The Williams Companies, Inc. verified
- Owner HQ
- 🇺🇸 United States, Tulsa
- Origin
- 🇺🇸 United States
- Category
- Energy › Oil & gas › Pipelines & midstream
- Parent ticker
- NYSE: WMB
- Last verified
- · 1 sources
About MountainWest
Williams' 2025 10-K says it owns 100 percent of MountainWest Pipelines Holding Company, an interstate gas transmission company with an approximately 2,200-mile FERC-regulated system and 8.4 MMdth/d of design capacity.
What Williams's annual report says about MountainWest
Sentences about MountainWest from Williams's latest annual filing[1], copied word for word.
NWP also contracts for natural gas storage services for approximately 3 Bcf at the Clay Basin underground storage reservoir with a Williams' affiliate, MountainWest.
MountainWest is an interstate natural gas transmission company that owns and operates an approximately 2,200-mile natural gas pipeline system which is regulated by the FERC.
During 2025, MountainWest placed the Overthrust Westbound Compression expansion project into service increasing firm transportation capacity by approximately 0.3 MMdth/d to its pipeline.
How often Williams names MountainWest in its annual report
A plain count of the times the name appears in the text of each annual report, not counting the start of a sentence. A brand that an owner writes about more is usually one it treats as central. The brand is named less often than it was three years earlier.
Ownership timeline of MountainWest
Where MountainWest sits in Williams
Controlling ownership as of . Brands grouped under the entity that owns them; large groups are collapsed.
Open the full Williams ownership tree →
See the full Williams brand portfolio (3) →
Other brands owned by Williams
Williams controls 3 brands on Brandtree, 3 of them in energy.
Also in energy
Other brands in pipelines & midstream, and who owns them
The 35 brands in pipelines & midstream on Brandtree belong to 21 owners. The largest is Energy Transfer, with 4; Williams has 3.
| Brand | Owner | Owner based in |
|---|---|---|
| Dakota Access Pipeline | Energy Transfer | 🇺🇸 United States |
| Dixie Pipeline | Enterprise Products | 🇺🇸 United States |
| Basin Pipeline | Plains All American | 🇺🇸 United States |
| Corpus Christi LNG | Cheniere | 🇺🇸 United States |
| Cenit | Ecopetrol | 🇨🇴 Colombia |
| Enbridge Mainline System | Enbridge | 🇨🇦 Canada |
| Columbia Pipeline Group | TC Energy | 🇨🇦 Canada |
| Aris Water Solutions | Western Midstream | 🇺🇸 United States |
About the owner: Williams
Williams is a publicly listed company headquartered in Tulsa, United States, founded in 1908. Brandtree records 3 brands under its control, and it is listed as NYSE: WMB.
Williams says in its 2025 Form 10-K that it was founded in 1908, is headquartered in Tulsa, Oklahoma, and owns an interest in and operates over 32,000 miles of pipelines. The filing describes Transco, Northwest Pipeline and MountainWest as its interstate natural gas transmission businesses, alongside gathering and processing and NGL operations.
🇺🇸 MountainWest and other American brands
Brandtree records a controlling owner for 2,399 brands that began in the United States. 461 of them (19%) are now controlled by a company headquartered in another country; MountainWest is not one of them.
- AES Ohio — AES 🇺🇸
- Agway Energy Services — Suburban Propane 🇺🇸
- Alabama Power — Southern Company 🇺🇸
- AmeriGas — UGI 🇺🇸
- American Transmission Company — WEC Energy Group 🇺🇸
- Arch Resources — Core Natural Resources 🇺🇸
Frequently asked questions
Who is the parent company of MountainWest?
The parent company of MountainWest is Williams, a publicly listed company headquartered in the United States.
Is MountainWest American?
Yes. MountainWest originated in the United States and its owner, Williams, is also headquartered in the United States.
Is MountainWest still owned by Williams?
Yes. As of 10 October 2026, MountainWest is still owned by Williams. The ownership record was last checked against primary sources on that date.
Sources (1) & corrections
Last verified . Every ownership fact above is backed by one of these primary documents. Numbers in brackets in the text refer to this list.
- [1] The Williams Companies, Inc. Annual Report on Form 10-K filed 2026-02-24 — SEC EDGAR, SEC Form 10-K, published 24 February 2026; retrieved 5 October 2026.
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