The period between the 1930s and the 1970s marked an era of development for Ohio Water Service Company. In 1973, the company merged with Consumers Water Company of Portland, Maine making Ohio Water Service Company a wholly owned subsidiary of Consumers Water Company. Ohio Water Service became known as Consumers Ohio Water Company in 1993. In March 1999, Consumers Water Company merged with Philadelphia Suburban Corporation (PSC) making COWC a subsidiary of one of the largest investor-owned water utilities in the nation. PSC was renamed Aqua America, Inc., in 2004 and COWC became Aqua Ohio, Inc.
