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 Web site to provide 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 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.

In 2002, PJM integrated Allegheny Power’s five-state transmission system into the PJM system. The achievement demonstrated that PJM’s proven wholesale market model could be implemented successfully in new regions.

Twenty one companies in Northern Illinois - including Chicago-based Commonwealth Edison (ComEd), a subsidiary of Exelon Corporation - fully integrate with PJM, adding 20 percent to the scope of PJM's operations and making PJM the largest transmission grid operator in the world based on a peak load of 87,000 megawatts on May 1, 2004.

On Oct. 1, 2004, American Electric Power (AEP) and Dayton Power & Light joined PJM, increasing peak load to 106,000 MW, generating capacity to 134,250 MW and miles of transmission lines to 49,300 miles. AEP is the largest electricity generator in the United States.

Duquesne Light joined PJM on Jan. 1, 2005, adding the Pittsburgh, Pa.-based utility's territory in western Pennsylvania to the PJM footprint.

On May 1, 2005, Dominion joined PJM, adding its Virginia and North Carolina territory to the PJM area, increasing peak load to 135,000 MW, generating capacity to 163,806 MW and miles of transmission lines to 56,070 miles.