The firm founded in 1892 as the Cleveland General Electric Co. by Charles F. Brush became the Cleveland Electric Illuminating Company (C.E.I.) just two years later and established its headquarters offices in the Cuyahoga Building on Public Square. C.E.I.'s stint in the Cuyahoga Building was short-lived, however. The company transferred its headquarters into the 75 Building, on the northwest corner of Public Square in 1914. C.E.I. outgrew its facilities at 75 Public Square as the demand for electrical power rose, and in 1956 broke ground to construct its own Illuminating Building right next door at 55 Public Square. C.E.I. signed a fifteen-year, $408,000 lease to occupy the first five floors of the Illuminating Building. Despite occupying all fourteen floors of the old 75 Building, the Illuminating Building offered 17% more space on those initial five floors alone. The monumental 1958 move included some 800 dolly-loads of office equipment and an additional 500 desks. Nevertheless, the move was completed in less than eighteen hours as workers never stepped foot outdoors thanks to existing pedestrian tunnels connecting one building to the other.
At the turn of the twentieth century, C.E.I. ran advertisements offering to wire homes with electricity for a price of $38.50, touting the benefits of domestic electricity, "Convenience-Cleanliness-Brightness-Luxury." Eventually, the company became famous for its 1940s-1960s ad campaign, which promoted Cleveland as "the best location in the nation." This ad campaign aimed to attract major industries to Cleveland, and promoted C.E.I.'s contribution to the overall welfare of Northeast Ohio by emphasizing its own role in expanding business, industry, job opportunities, and improving the overall quality of life.
A massive workforce strike erupted in the midst of the "best location in the nation" ad campaign. On April 24, 1957 the members of Utility Workers Local 270 voted a resounding 1,754-63 in favor to strike against C.E.I. Workers demanded that C.E.I. do away with its right to make job changes and transfers without informing the union, as well as re-negotiate wages to obtain a "substantial" increase. The strike ended on May 7 after a grueling fifteen-hour negotiation. The fifteen-day strike became the longest of its kind in C.E.I.'s prominent history, which had only witnessed a single six-hour strike in 1945. Resolutions involved a new two-year contract with a general wage increase of five percent, or the equivalent of ten to fifteen cents per hour.
During the 1960s, C.E.I. became pressured to respond to the increasing demand for nuclear power, and began to invest in nuclear power plants in collaboration with Toledo Edison in 1970. The decade of the 1970s witnessed the widespread energy crisis, which drove up the price of coal dramatically. Likewise, domestic energy costs for consumers skyrocketed, and C.E.I. lost a considerable amount of customers. In order to stay afloat, C.E.I. merged with Toledo Edison in 1986 to form Centerior Energy. A little over a decade later in 1997, Centerior Energy combined with Ohio Edison and Penn Power to form FirstEnergy, which controls the electric system for northern Ohio and western Pennsylvania.