Hurricane Agnes was a relatively weak storm when it hit Florida on June 19, 1972. But by the time it dissipated a week later over Pennsylvania, it had become one of the costliest tropical systems in history.

After coming ashore, Agnes tracked northeastward over land and weakened, but it restrengthed as it emerged off the Carolina coast. On June 22, 1972, Agnes dumped more than 4 inches of rain on Wilmington, the city's rainiest June day on record. All told, Agnes brought 3 to 5 inches of rain to Delaware and the immediate Philadelphia area.

But farther north and west, 10 to 15 inches of rain fell. Half of Harrisburg was flooded by the waters of the Susquehanna. The Schuylkill River at Reading, PA, crested 18 feet above flood stage.

Even at Fairmount Dam in Philadelphia, the flooding from Agnes remains the worst on record, exceeding even that of Floyd. And to this day, Agnes remains Pennsylvania's worst natural disaster.