WGL Holdings, Inc., through its subsidiaries, engages in the sale and delivery of natural gas, and provides energy-related products and services. It operates in three segments: Regulated Utility, Retail Energy-Marketing, and Design-Build Energy Systems. The Regulated Utility segment delivers natural gas to retail customers; and operates and owns full and partial interests in underground natural gas storage facilities, including pipeline delivery facilities located in and around Hampshire County, West Virginia. As of September 30, 2011, it had approximately 664 miles of transmission mains, 12,517 miles of distribution mains, and 13,331 miles of distribution services, as well as the storage capacity for approximately 15.0 million gallons of propane for peak-shaving. The Retail Energy-Marketing segment sells natural gas and electric commodity directly to residential, commercial, and industrial customers. It served approximately 172,000 residential, commercial, and industrial natural gas customers and approximately 183,000 residential, commercial, and industrial electricity customers located in Maryland, Virginia, Delaware, and the District of Columbia. The Design-Build Energy Systems segment provides design-build energy efficient and sustainable solutions to government and commercial clients. This segment focuses on upgrading the mechanical, electrical, water, and energy-related systems of government and commercial facilities by implementing both traditional, as well as alternative energy technologies, primarily in the District of Columbia, Maryland, and Virginia. The company was founded in 1848 and is headquartered in Washington, the District of Columbia.