An official post-mortem of the outage by a US-Canada joint task force:
Final Report on the August 14, 2003 Blackout: Causes and Recommendations (pdf)
Via Dan Luu’s collaborative postmortem list, where “gnomon-” reports:
A power outage in Ohio around 1600h EDT cascaded up through a web of systemic vulnerabilities and process failures and resulted in an outage in the power grid affecting ~50,000,000 people for ~4 days in some areas, and caused rolling blackouts in Ontario for about a week thereafter.