PJM began in 1927 when three utilities, realizing the benefits and efficiencies possible by interconnecting to share their generating resources, formed the world’s first continuing power pool. Additional utilities joined in 1956, 1965 and 1981. Throughout this time, PJM was operated by a department of one member utility.

In 1962, PJM installed its first online computer to control generation. PJM completed its first Energy Management System (EMS) in 1968. The EMS is the information technology system that makes it possible to monitor transmission grid operations in real time. In 1996, PJM launched its first website to provide its members with current system information.

PJM began the transition to an independent, neutral organization in 1993 when the PJM Interconnection Association was formed to administer the power pool. In 1997, PJM became a fully independent organization. At that time, membership was opened to non-utilities and an independent Board of Managers was elected.

On April 1, 1997, PJM opened its first bid-based energy market. Later that year the Federal Energy Regulatory Commission (FERC) approved PJM as the nation’s first fully functioning independent system operator (ISO). ISOs operate, but do not own, transmission systems in order to provide open access to the grid for non-utility users.

Later, the FERC encouraged the formation of regional transmission organizations (RTOs) to operate the transmission system in multi-state areas and to advance the development of competitive wholesale power markets. PJM became the nation’s first fully functioning RTO in 2001.

From 2002 through 2005, PJM integrated a number of utility transmission systems into its operations. They included Allegheny Power in 2002, Commonwealth Edison, American Electric Power and Dayton Power & Light in 2004 and Duquesne Light and Dominion in 2005. In 2011, American Transmission Systems, Inc. (ATSI), the transmission affiliate of FirstEnergy, and Cleveland Public Power (CPP) were integrated into PJM. These integrations expanded the number and diversity of resources available to meet consumer demand for electricity and increased the benefits of PJM’s wholesale electricity market.