Emergency officials promised to deliver needed supplies such as water and bedding, but found going difficult because of debris-strewn roads, washed out highways and power outages.
Utility companies said more than 1.3 million homes and businesses still had no electricity Saturday from Florida north to Pennsylvania.
Ivan, which struck the Gulf coast early Thursday, was the deadliest hurricane to hit the United States since 1999 when Floyd killed 57 - 56 in the United States and one in the Bahamas. Ivan has been blamed for 70 deaths in the Caribbean and 44 in the United States, 16 of them in Florida.
More than a dozen people remained missing Saturday, but it wasn't clear whether they were in danger or had simply evacuated without notifying relatives, said Sonya Smith, spokeswoman for the Escambia County emergency operations center. The county had 72 reports of looting, with 15 arrests.
Shirley Rogers, a 64-year-old retired nurse, put on gloves and black rubber boots Saturday as she and her daughter sifted through what possessions they could at her home in the town of Gulf Breeze. One wall of her single-story home was completely missing.
"I lost everything," she said. Her property was covered in bricks and other debris, along with puddles of brown water and the stench of sewage from a treatment plant that leaked into the bay.
Officials said it would take weeks for power, sewer and water services to be restored in parts of northwestern Florida, another storm-ravaged section of a state already hit by Hurricanes Charley and Frances during an otherwise steamy summer. Those storms left Floridians without power for days.
Insurance experts put Ivan's damage at anywhere from $3 billion to $10 billion. Hurricanes Charley and Frances had combined estimated insured damages between about $11 billion and $13 billion.
"I think the biggest problem that Florida is going to face is fatigue," Michael Brown, director of the Federal Emergency Management Agency, said Saturday. "When you think about these three hurricanes, the continuing rains and storms, and just the heat, people are going to get worn out."
The business of rebuilding was under way in earnest on Saturday. Road crews worked furiously to bulldoze debris to the side of byways in Florida, while several major thoroughfares - including a buckled interstate bridge - stayed closed to travelers. Other streets remained an obstacle course of tree limbs and power lines.
Utility workers managed to restore a major generating plant and some 150 miles of transmission lines, but "there is still an unbelievable amount of hot, hard and dangerous work ahead," Gulf Power spokesman John Hutchinson said.
Florida Gov. Jeb Bush offered a grim assessment of the damage from Ivan, which struck the coast with the sledgehammer force of 130-mph winds and a major storm surge.
"The power issue is going to be a bigger issue than in Charley or Frances," Bush said Friday. "Living without air conditioning, it's not just an inconvenience, that's a health issue for a lot of people."
President Bush - the governor's brother - was expected to visit the area Sunday, the president's third trip to review hurricane damage in Florida.
Naval Air Station Pensacola suffered massive damage during the storm, estimated in the hundreds of millions of dollars, the Navy said Friday. Ninety percent of the buildings on the base suffered "significant" damage, although no one was reported injured, according to a Navy statement.
Some military aircraft stationed in the Pensacola area had been flown out ahead of the storm, but other aircraft left behind may have been damaged.
As the broad area of rain that remained from Ivan streamed off through New England on the way to the North Atlantic, the National Weather Service predicted the Ohio River would crest Sunday in the Wheeling, West Virginia vicinity at 46 feet, about 10 feet above flood stage and close to its record.
By early afternoon Saturday, it was already at 41.7 feet, the National Weather Service said. The river had submerged the northern tip and southern half of the city's Wheeling Island, which holds residential neighborhoods and Wheeling Island Racetrack and Gaming.
"We've been plucking people out of here left and right," firefighter David Schaffer said. "People are waiting until the last minute, and then they see the water come up and they get panicked."
Downriver, residents were urged to evacuate parts of Moundsville, and big flood gates were closed at Parkersburg, where the river was expected to crest Sunday at five feet above flood stage.
All around West Virginia, flooding and mudslides had blocked 207 roads and damaged hundreds of houses, authorities said.
Upriver in western Pennsylvania, downtown Pittsburgh's Point State Park was underwater Saturday where the Monongahela and Allegheny rivers join to form the Ohio. Dozens of boats that had broken free of their moorings were floating down the fast-rushing rivers.
Elsewhere, streams had started to recede in hard-hit western North Carolina as others rose in New York.
Parts of northern New Jersey and eastern New York measured 5 inches of rain Saturday. A mobile home park had to be evacuated because of flooding in Ravena, N.Y., 13 miles south of Albany.
Williamsport, Pa., collected 6.5 inches of rain in 24 hours and Pittsburgh got a record 5.95 inches Friday.
Across the Ohio River from West Virginia, Ivan also had caused flooding in eastern Ohio. About 1,500 residents of Belmont County were out of their homes on Saturday, and some 27,000 were without drinking water because of line breaks, said Julie Hinds, a spokeswoman for the Ohio Emergency Management Agency.
In the village of Amesville, Ohio, 115 youngsters spent the night in their elementary school because of flooded roads. The children slept on carpeted classroom floors, wrapped in blankets that the Red Cross delivered by boat, said librarian Patti McKibben.
After devastating parts of Alabama and the Florida Panhandle, Ivan poured as much as 12 inches of rain Friday on North Carolina's mountainous western tip, which was still sodden from Frances' floods a week earlier.
As of Saturday morning, 119 primary and secondary roads were still impassable in western North Carolina, including a stretch of Interstate 40 spanning the North Carolina-Tennessee line, state officials said.
Ivan weakened after coming ashore, but continued to spin off tornadoes and cause flooding and mudslides in the southeastern United States. The storm caused heavy rain Saturday all the way to New England.
Ivan was downgraded to a tropical depression by the time it reached North Carolina late Thursday, as was Hurricane Frances when it arrived Sept. 7. North Carolinians had little time to recover between the storms.
Two of the latest deaths blamed on Ivan were two people killed Saturday in Maryland when a tree was blown into a mobile home.
Meanwhile, forecasters said Hurricane Karl was moving in the central Atlantic on Saturday but posed no immediate threat to land.
The National Hurricane Center in Miami said Karl, the seventh hurricane this season, had top sustained winds near 110 miles per hour and was expected to get stronger on Sunday.
Karl came on the heels of Tropical Storm Jeanne, which was near the southeastern Bahamas, and had the potential to gain strength, forecasters said.
Karl was the 11th named storm of the Atlantic hurricane season, which runs from June 1 to Nov. 30.