Friday marks 23 years since the Northeast blackout

NEW YORK (CBS, KYMA) - On August 14, 2003, a massive power outage spread through parts of the Northeast and Midwest United States and most parts of the Canadian province of Ontario.

The blackout began just after 4 p.m. Eastern, shutting off power from New York City to Toronto, affecting an estimated 55 million people.

Traffic lights shut off in Times Square and New York's subway system came to sudden halt.

Essential services remained in operation in some of these areas, but in others, backup generation systems failed.

Telephone networks generally remained operational, but the increased demand triggered by the blackout overloaded many circuits. Water systems lost pressure in several cities, forcing boil-water advisories to be put into effect.

Most places restored power by midnight, while the New York City Subway resumed limited services around 8 p.m. Eastern.

The cause of the blackout was determined to be a software bug in the alarm system at the control room of FirstEnergy, an energy company based in Akron, Ohio.

The software bug rendered operators unaware of the need to redistribute load after overloaded transmission lines drooped into foliage.