Stakeholders for San Antonio's Andeavor and Ohio's Marathon Petroleum Corp. approved the merger in separate votes.
El Paso's oil refinery and Howdy's convenience stores are expected to be under new ownership on Oct. 1.
That's when the previously announced sale of San Antonio's Andeavor — which owns the El Paso refinery, a Gallup, N.M., refinery, and Howdy's stores — to Ohio's Marathon Petroleum Corp., is scheduled to be completed.
In El Paso, 873 people work at Andeavor's operations.
On Monday, the majority of stockholders for both companies voted, in separate meetings, to approve the merger, which was announced April 30.
Marathon is buying Andeavor for $23.3 billion.
The combined companies — to become the largest oil refining company in the United States — will keep the Marathon name, and continue to be headquartered in Findlay, Ohio, which is near Toledo. The merged companies also will retain offices in San Antonio.
The El Paso refinery, on Trowbridge Drive in East Central El Paso, employs 473 people; El Paso-area Howdy's stores employ 400 people; and 230 people work at the Gallup refinery, Andeavor officials reported.
Gary Heminger, Marathon chief executive officer, will be CEO of the merged companies.
Gregory Goff, Andeavor CEO, will become executive vice chairman —overseeing Marathon's information technology, commercial and business development, and strategy and corporate affairs.
"As we look forward, we remain focused on the tremendous potential this combination will bring our shareholders and are excited to begin executing our strategy to transform our company and realize our expected synergies," Heminger said in a statement released Monday.
The El Paso and Gallup refineries and Howdy's stores became part of Andeavor June 1, 2017, when it bought El Paso-based Western Refining for $5.8 billion.
"Although it is too soon to know for certain if there would be personnel changes at the El Paso refinery, it was acknowledged early on that it takes skilled, experienced people to operate our refineries, and we anticipate a need for the vast majority of our current refining employees," Chuck Rice, Marathon's director of public and state government affairs, said in an email.
C. Tracy Case, currently general manager of Marathon's Garyville, La., refinery will become senior vice president of the merged companies' Western refining operations, which will be based in San Antonio, and oversee eight refineries, including El Paso and Gallup.
El Paso billionaire Paul Foster, Western Refining's founder, and Jeff Stevens, Western CEO when the company was sold, are on Andeavor's board of directors. However, Foster and Stevens will not be on the Marathon board of directors. Goff, the Andeavor CEO and board chairman, two other Andeavor board members, Susan Tomasky and Edward Galante, and Kim Rucker, Andeavor general counsel, will be on the Marathon board.