Oklahoma Natural Gas Company was founded on October 12, 1906 by businessmen
Dennis T. Flynn and Charles B. Ames. During the spring and fall of 1907, the company built a gas pipeline from
Osage County to
Sapulpa and Oklahoma City. From the acquisition, Oneok acquired roughly 1,575 Western Resources employees as well as the 624,000 customers in Kansas and 36,000 customers in northeast Oklahoma. In 1999, Oneok agreed to acquire
Southwest Gas, a
Las Vegas based natural gas company, for $1.8 billion. In January 2000, Oneok terminated the pending merger of the two companies, and Southwest Gas filed a lawsuit against Oneok. Judge
Roslyn O. Silver dismissed two of the cases against Oneok in June 2001, and Oneok agreed to pay
Southern Union $3 million to settle the remaining case. In October 2002, Oneok acquired the Texas division and assets of
Southern Union Gas for $420 million. Oneok renamed the company to
Texas Gas Service when the acquisition was completed. The deal also gave Oneok a controlling interest in Northern Border Partners, which had a master limited partnership on 6,600 miles of pipeline, five natural gas processing plants, and two fractional plants. In November 2021, Oneok resumed construction of its natural gas processing facility Demicks Lake III plant in
McKenzie County, North Dakota which was originally delayed due to the
COVID-19 pandemic. The Demicks Lake III plant was later completed and began operations in February 2023. In July 2022, a Oneok gas plant in
Medford, Oklahoma exploded, causing no injuries but temporarily expelling roughly 1,000 residents from their homes. In January 2023, Oneok reached an insurance settlement payment of $930 million and the company announced plans to transition gas
fractionation operations away from the Medford plant. In September 2023, Oneok acquired
Magellan Midstream Partners for $18.8 billion. Included in the acquisition for Oneok was the Magellan-owned East Houston terminal and crude oil trading hub, facilities in
Galena Park, Texas and
Seabrook, Texas, and a terminal in
Pasadena, Texas. In May 2024, Oneok agreed to acquire Gulf Coast NGL Pipelines from Easton Energy for $280 million. The deal included 450 miles of pipelines located in Texas and the Louisiana Gulf Coast. The company expanded its operations in the Permian Basin through two acquisitions in late 2024. ONEOK acquired Medallion Midstream, a crude oil gathering and transportation company and a controlling stake in EnLink Midstream, an oil and natural gas infrastructure company. The company continued expansion into the Permian Basin in May 2025, when it gained full ownership of the Delaware Basin JV, which it previously operated as a joint venture with NGP XI Midstream Holdings. Through the acquisition Oneok gained operational control of infrastructure used to collect and process natural gas in the Delaware Basin that has a processing capacity of around 700 million cubic feet per day. ==Operations==