SemGroup is a transporter of oil and natural gas through pipelines from refineries to end users, an operator of oil terminals, as well as the manufacturer and seller of asphalt. The company began trading on the New York Stock Exchange under the symbol 'SEMG' in 2010. The company was originally founded in 2000 and as of 2007 was the 18th largest private company in the US, but filed for bankruptcy in 2008. As of December 2009, the company had restructured and emerged from bankruptcy at a reduced size. The company's headquarters are in Tulsa, Oklahoma.

SemGroup LP was founded in 2000. On July 9, 2007 SemGroup announced that it would establish a publicly traded affiliate, SemGroup Energy Partners LP, who would be traded on NASDAQ, under the symbol SGLP. This affiliate company was delisted from NASDAQ effective February 20, 2009. SemGroup Corporation later began trading on the NYSE in 2010.

In July 2008, SemGroup ran into liquidity problems and warned that it may have to file for bankruptcy as part of a financial restructuring. Adding to SemGroup's troubles, hedge funds run by Alerian Capital Management and Elliot Associates exercised the terms of a secured loan made to SemGroup and took over the general partnership interest in SemGroup Energy Partners LP. On July 22, 2008, Semgroup, LP filed for Chapter 11 bankruptcy protection in U.S. Bankruptcy Court in Wilmington, Delaware. The company listed both debts and assets of more than $1 billion.

New York billionaire John Catsimatidis then became engaged in efforts to take over SemGroup, and he gained control over a majority of the company's management committee. He was met by opposition from the company's existing management, who argued for selling off at least some of the company's assets, while Catsimatidis stated his intention to keep the company together. On February 11, 2009 Catsimatidis was sued by a group of SemGroup executives, seeking removal of Catsimatidis and his allies from the committee. In turn, the company and its unsecured creditors committee sued former CEO Tom Kivisto and former CFO Gregory C. Wallace, seeking return of $362 million that they claim the defendants used for their own transactions and benefits.

In April 2009, former FBI director Louis Freeh released a report on the circumstances surrounding the SemGroup bankruptcy. In July, Catsimatidis and the company reached a settlement, pursuant to which Catsimatidis acquired a piece of SemGroup's asphalt business and dropped his competing plan for the company's proposed reorganization.

On December 1, 2009, SemGroup exited bankruptcy under a new corporate structure, eliminating its master limited partnership and becoming a publicly traded company focused on asphalt manufacture and marketing and on oil and natural gas storage and transport, with about 140 employees in Tulsa and 1,000 overall. On the same day, the former SemGroup Energy Partners LP adopted a new name, Blueknight Energy Partners LP; Blueknight is now separate in ownership and assets (although sharing a pipeline system with SemGroup).

SemGroup Corporation's common stock (NYSE: SEMG) was listed on the New York Stock Exchange as of November 11, 2010, and two of its representatives were invited to ring the NYSE opening bell on December 17, 2010, as the company assumed what a Wall Street Journal reporter described as "a new identity as a conservative middleman to the Midwestern oil and gas industry."

Meanwhile, global oil trader Vitol Group took control of Blueknight (the former SemGroup Energy Partners LP). In October 2010, Vitol made a deal to add Charlesbank Capital Partners as a second general partner; this led to public charges, by an investment fund associated with billionaire Michael Dell, that the transaction was improper self-dealing intended to take money from Blueknight's existing limited partners. Vitol denied these charges.

SemGroup LP is engaged in diversified services for the North American crude oil and refined products industry. Operations include gathering, transporting, marketing and hedging services. SemGroup owns and operates carrier pipelines, oil terminals, oil transport and service trucks, pipeline injection stations and terminal storage in Oklahoma, Louisiana, Kansas, and Texas. Canadian operations are located in Alberta, British Columbia, and Saskatchewan. The company is based in Tulsa, Oklahoma, United States.

SemLogistics is a business unit of SemGroup based in Wales that operates one of the largest petroleum products storage facilities in the United Kingdom, accounting for nearly 25 percent of the UK’s independent multiproduct storage. Storage capabilities include gasoline, gasoline blendstocks, naphtha, jet fuel, gas oil and diesel, as well as crude oil.

SemCAMS is a business unit of SemGroup based in Calgary, Alberta. SemCAMS operates four gas processing plants located in the Western Canadian Sedimentary Basin. SemCAMS offers midstream service options for wet or dry, sweet or sour gas gathering and processing, as well as dehydration, field compression and sulfur forming and handling.

SemMaterials is the business unit of SemGroup primarily responsible for asphalt and emulsion production. Frank Panzer ran the business unit from 2005 until 2008. Osvaldo ("Ozzy") Speranza now serves as general director for SemMaterials México. SemMaterials has a presence in all Mexican territories, working with local and federal agencies as well as some of the most important contractors and concessionaries.

As an industry leader, SemMaterials México has a portfolio of paving materials that helps customers build longer-life roads and provides them solutions for improved maintenance and repairs.

Houston Fuel Oil Terminal Company was acquired by SemGroup in July 2017. Often referred to as 'HFOTCO,' the business unit operates one of the largest oil terminals in the U.S. HFOTCO is located in the Houston Ship Channel on the U.S. Gulf Coast.

Rose Rock Midstream was a master limited partnership formed by SemGroup that traded under the ticker symbol 'RRMS.' SemGroup announced in May 2016 an agreement to acquire all of the remaining outstanding units of Rose Rock Midstream that it did not already own in an all stock-for-unit transaction that closed in September of that year. Rose Rock currently operates as a business unit under SemGroup.

Thomas L. Kivisto co-founded SemGroup and served as its President and Chief Executive Officer. Another co-founder was Gregory C. Wallace, who served as Vice President, Chief Financial Officer, and Secretary. In 2008, Terry Ronan replaced Kivisto as President and CEO. In September 2009, SemGroup announced a new leadership team, to be led by a new president and CEO, Norm Szydlowski, an experienced oil industry executive who had previously served as president and CEO of Colonial Pipeline Co. A new board was also announced, to be chaired by John F. Chlebowski, a director of NRG Energy, Inc. and previously president/CEO of GATX Terminals.

Current President and CEO Carlin G. Conner was later named to the company's top role, taking over the position on April 1, 2014. Thomas R. McDaniel became chairman of the SemGroup board of directors on Jan. 1, 2017. McDaniel has served as a director of SemGroup since 2009.