Commonwealth Edison, commonly known by syllabic abbreviation as ComEd, is the largest electric utility in Illinois, and the in Chicago and much of Northern Illinois. Its service territory stretches roughly from Iroquois County on the south to the Wisconsin border on the north and from the Iowa border on the west to the Indiana border on the east. For more than 100 years, Commonwealth Edison has been the primary electric delivery services company for Northern Illinois. Today, ComEd is a unit of Chicago-based Exelon Corporation, one of the nation's largest electric and gas utility holding companies. ComEd provides electric service to more than 3.8 million customers across Northern Illinois. , ComEd has interconnections with We Energies, ITC Midwest, Ameren, American Electric Power, Northern Indiana Public Service, and MidAmerican Electric (MEC). History Founding The earliest predecessor of Commonwealth Edison was the Isolated Lighting Company, established in early 1881 by George H. Bliss as a subsidiary of Thomas Edison's company to sell small Edison-patented generators and lighting systems, each serving one building or several nearby buildings. In 1882, this company was taken over by the Western Edison Light Company, which was chartered by several prominent Chicagoans to not only take over Isolated Lighting's role as Edison's agent in Chicago, but also to develop a central station electric system. Western Edison installed the first incandescent lighting in a Chicago home, that of stockholder John W. Doane, in 1882, and it was first lit on November 10 of that year. Chicago Edison In March, 1887, John M. Clark (president of Western Edison), Robert Todd Lincoln, and John B. Drake obtained a franchise from Chicago to distribute electricity in the downtown area, bounded by North Avenue, 39th Street, and Ashland Avenue. They then formed the Chicago Edison Company, which took over all of Western Edison's business on July 2, 1887. Chicago Edison's first central generating station, designed by chief engineer Frederick Sargent, opened at 139 (later 120) West Adams Street in August, 1888. This first station was intended to serve an area bounded by Harrison Street, Market Street and Water Street (both now Wacker Drive), and Michigan Avenue, and served this area with an Edison-patented direct current system until it closed in 1914 or 1915. The Samuel Insull Era By 1892, Chicago Edison's load had grown to 3,200 kilowatts, the full capacity of its generating station. Its growth showed no sign of slowing, especially with