PG&E Corporation, through its subsidiary, Pacific Gas and Electric Company, operates as a public utility company in northern and central California. It engages in electricity and natural gas distribution; electricity generation and transmission; and natural gas procurement, transportation, and transmission and storage operations. The company owns and operates electricity generation facilities, transmission and distribution lines, and substations; and an integrated natural gas transportation, storage, and distribution system, as well as has underground natural gas storage fields in California. It serves residential, commercial, industrial, and agricultural customers. As of December 31, 2012, the company served approximately 5.2 million electricity distribution customers and 4.4 million natural gas distribution customers, as well as operated 18,100 circuit miles of interconnected transmission lines and 141,000 circuit miles of electricity distribution lines; and 42,400 miles of distribution pipelines, 6,400 miles of backbone and local transmission pipelines, and 3 underground storage fields for natural gas. The company was founded in 1905 and is based in San Francisco, California.