Agnes floodwaters collapsed the Engleside Bridge, south of the city, into the raging Conestoga River.
A boat floats down a street in Marietta on June 23, 1972.
An extremely heavy flow of water passes over the Conowingo Dam on the Susquehanna River on June 24, 1972.
Front Street and much of Marietta's downtown was under water after heavy rains from Tropical Storm Agnes caused widespread flooding.
A firefighter uses a boat to rescue residents on Main Street in Manheim on June 22, 1972, after the Chiques Creek raged through the borough as Tropical Storm Agnes brought heavy rains.
The wrecked Engleside bridge at Lancaster is seen.
The remains of the railroad bridge across the Susquehanna River at Marietta are seen.
The wreckage of the Hunsicker covered bridge near the steel bridge on New Holland Pike is seen.
Forty years ago the "A" storm of the hurricane season arrived here on June 22. It was a relatively weak one when it first made landfall in Florida.
But as Hurricane Agnes started to make its way up the east coast and converged with another low pressure system over Pennsylvania, it reached its full intensity and became the costliest natural disaster in the United States at that time.
The damage and death toll was the highest in Pennsylvania, with about 50 deaths and $2.3 billion in losses.
"We haven't had an event that can match Agnes," Eric Horst, director of the Weather Information Center at Millersville University, said.
"The flooding last fall as a result of Tropical Storm Lee didn't even come close. The Agnes event is so far above anything we've ever seen," Horst said.
Today marks the 40th anniversary of Tropical Storm Agnes, the 1972 deluge that is the worst natural disaster ever to hit the state of Pennsylvania.
The damage was so extreme the entire state was declared a disaster area.
With the 2012 hurricane season officially under way, many are likely remembering the storms of the past and praying for the best.
"Agnes was a traumatic experience for us," Dave Fenicle, Manheim Borough Authority executive director, said.
Fenicle was a young boy when Agnes hit the region. He recalled the effects of the storm in the Palmyra area where his grandfather lived.
"My grandfather's house was a two-story home, and it had water all the way up to the second floor," he said.
Residents in low-lying areas were ordered to evacuate. Roads and streets turned into swamps and rivers, water ripping through them with incredible force.
"Obviously it could happen again next year or it could be another 40 years before we have another big one.
"With Lee, the problem was that the water came up so quickly that no one was prepared," Fenicle said.
Thousands of residents were ordered to flee the rising Susquehanna River as the remnants of Lee clobbered the area with heavy wind and rain.
By the time Lee eased its grip on the county, the Susquehanna River had reached its fourth-worst flood stage in its history.
"The Susquehanna crested at 58.2 feet during Lee," Horst said. "By comparison, it crested at 64.5 during Agnes."
Marietta Borough Council President Miriam Fletcher noted two major concerns.
"We are always worried about water levels causing a back-flow into the stormwater drainage system," Fletcher said.
"And how to handle Evans Run, which runs through the borough and into the river. We have seen an increase in runoff," she said.
Rising water presented a great challenge last fall to areas still reeling from the effects of earlier storms.
"We are prone to flooding here with the Conestoga and the Susquehanna rivers around us," Horst said.
However, not everyone is overly concerned about it.
"Instead of fearing, we need to be prepared … just in case," Fenicle said.
"It might be a little difficult getting in and out because of water, but most of the people who live in those areas know how to handle it," Fletcher said.
"What I've learn from the past storms is to be better prepared for the next one and to prevent the loss of life," Fenicle said.
