Southwest Gas Holdings Inc. has completed its nearly $2 billion acquisition of Dominion Energy Questar Pipeline LLC, a move that activist investor Carl Icahn had attempted to thwart. 

Questar and its affiliates, which operate 2,160 miles of FERC-regulated interstate natural gas pipelines in the Rocky Mountain region, is to be rebranded as subsidiary MountainWest Pipelines Holding Co. The rebranding is to occur by June, said Southwest Gas.

“Natural gas pipelines are essential to the nation’s energy future, which includes alternative sources such as renewable natural gas and hydrogen blended gas, and MountainWest brings increased scale and diversification to our business portfolio,” said Southwest Gas CEO John Hester. “MountainWest will focus on adding value by accelerating...