Iroquois Gas Transmission System was created in 1985 as a cooperative venture to provide the Northeast with supply diversity and safe, reliable delivery of cost-effective and clean-burning natural gas.

| Partner Company | Affiliation | Ownership |
| TC PipeLines, LP | TC PipeLines GP, Inc.* | 49.34% |
| TransCanada Iroquois LLC | TransCanada PipeLine USA Ltd.* | 0.66% |
| Iroquois, Inc. | Eastern Energy Gas Holdings, LLC** | 24.07% |
| Iroquois GP Holding Company, LLC | Iroquois, Inc.** | 25.93% |
| *Subsidiary of TC Energy **Subsidiaries of BHE GT&S, LLC, a Berkshire Hathaway Energy Company |