Early settlers called the Susquehanna River "a mile wide and a foot deep." The folk saying hints at the forces behind a river that is, in fact, exceptionally likely to flood.

And flooding it is, with record or near-record levels along its path from New York state, through Pennsylvania and into Chesapeake Bay in Maryland after a wet summer that included tropical storms Irene and now Lee.

"The Susquehanna is one of the most flood-prone rivers in America," said Chris Duffy, a professor of civil and environmental engineering at Penn State University. "Here, you encounter the bedrock pretty quickly."

The Susquehanna began receding in Binghamton, N.Y., and northeastern Pennsylvania on Friday, hours after cresting just beneath the top of levees protecting some cities from the worst of the flooding. But other, unprotected communities downstream were inundated with water, with several thousand homes submerged — some swept off their foundations.

In Pennsylvania's Luzerne County, many homes were inundated up to the second floor, county commissioner Maryanne Petrilla said.

In Wilkes-Barre, 75,000 people remained under mandatory evacuation, although the 41-foot-high levees were able to weather the Susquehanna crest at 38.83 feet. Some low-lying areas experienced flooding, but much of the town appears to have been spared.

"The levees are holding, but we are coming upon some issues," Petrilla said. "They're showing some signs of weakness."

Crews were dispatched early Friday to patch up weak parts. "If the levees give way, flooding could be much greater," Petrilla said. "The next 24 hours are critical."

In West Pittston, north of Wilkes-Barre and without levees, at least 500 homes were underwater, Petrilla said.

"They were unprotected," she said. "The water came so fast that they got flooded out."

In Wyoming County, about 4,200 families were affected by flooding — some because water streamed into their basements, others because houses were swept off foundations.

Rescue crews took to boats to pull out scores of people stranded in their cars; rescuers saved a family of three seconds before their home in Meshoppen was swept downstream, said Dave Carichner, the county's deputy emergency-management coordinator.

The Susquehanna has flooded 14 times since 1810 — an average of every 15 years. The worst in modern times was in 1972, when remnants of Hurricane Agnes dumped biblical rains, killing 72 people and causing $2.8 billion in damage (more than $14 billion in today's dollars), according to the Susquehanna River Basin Commission.

While not as deadly as that event, this year's flooding is worse, Carichner said.

At least four people have been killed in Pennsylvania, said Cory Angell, a spokesman for the state's emergency-management office.