Steve McCausland of the Maine Public Safety Department says the girl's name isn't being released but that she was from New York state. The girl was one of three people plucked from the water by rescuers. The other two were a man and a 12-year-old girl who were hospitalized.
The Coast Guard says the girl was unresponsive when she was rescued.
The National Hurricane Center says the center of the hurricane was about 230 miles west of Newfoundland on Sunday night.
A large wave fueled by Hurricane Bill swept spectators out to sea at a Maine park Sunday as the storm-churned surf attracted onlookers and daredevils along the Eastern Seaboard.
A man, a woman and a 7-year-old girl were pulled from the sea near Acadia National Park, Coast Guard Petty Officer 2nd Class Shane Coxon said, and rescue crews were searching for others believed to be lost in the waves.
"This is absolutely the effects of Hurricane Bill" coupled with the effect of high tide, park ranger Sonya Berger said.
The girl was unresponsive when she was rescued, the woman appeared to have a broken leg and the man had a previous heart condition that appeared to be acting up, Coxon said.
The hurricane was also blamed for the death of a 54-year-old swimmer Saturday in Florida. Volusia County Beach Patrol Capt. Scott Petersohn said Angel Rosa of Orlando was unconscious when he washed ashore in rough waves fueled by Bill at New Smyrna Beach, along the central Florida coast. He was pronounced dead at a hospital.
Lifeguards there also rescued a handful of other swimmers believed to have suffered spinal injuries.
The center of the hurricane was about 400 miles west-southwest of Newfoundland late Sunday afternoon, according to the National Hurricane Center. Its maximum sustained winds had dropped to 75 mph, and it was moving northeast at 35 mph. The storm is expected to continue to lose strength as it moves over cooler waters.
The three rescued in Maine were part of an early afternoon crowd of thousands who lined the national park's rocky shoreline to watch the high surf and crashing waves.
James Kaiser of Bar Harbor was taking photographs when he heard shouts that people had been swept into the 55-degree water at the park's Thunder Hole, a popular tourist attraction where waves often crash into a crevasse and make a thundering sound while splashing high in the air.
"I could see two people's heads bobbing in the water," Kaiser said. He said he thought they would be bounced back to shore because the waves were coming in so hard but that instead the current took them away from shore.
Kaiser said many people didn't even move when they were splashed by the waves and instead seemed to laugh it off.
Others on shore suffered minor injuries after being knocked to the rocks by the waves, Acadia National Park Chief Ranger Stuart West said.
The search on the water for others believed to be missing was due to be called off at sunset, West said. The waves were running 10 to 12 feet high with 25-knot winds along the coast, Coxon said.
Along Nova Scotia's Atlantic coast, the storm delivered steady downpours and fierce winds, forcing flight cancellations and temporary road closings. Bill ripped branches from trees in Halifax and elsewhere, and there was some localized flooding. Some 40,000 Nova Scotia Power customers lost power, but it was gradually being restored Sunday.
Craig MacLaughlan, CEO of Nova Scotia's Emergency Management Office, said no major damage has been reported in the province.
The storm drew onlookers hoping to catch a glimpse of crashing waves as it marched through Atlantic Canada.
Despite repeated warnings, people gathered in Peggy's Cove, Nova Scotia, and along the boardwalk in downtown Halifax as swells grew steadily in strength and size.
"So far, it's pretty wild," said Heather Wright, who was walking along the Halifax harbor.
In Massachusetts, President Barack Obama and his family arrived on Cape Cod on Sunday afternoon for vacation after the storm had passed well to the east.
Several people had to be rescued from the water in Massachusetts, including a couple of kayakers who got stranded in the heavy seas off Plymouth, said Peter Judge, a spokesman for the Massachusetts Emergency Management Agency.
He said strong rip tides and beach erosion were the biggest concerns Sunday.
"Our biggest thing right now is just the rough surf," he said.
Dozens of people showed up at South Beach on Martha's Vineyard with their cameras and camcorders to watch the big waves and churning Atlantic.
Tony Dorsey of Gofftown, N.H., has a camp on the Vineyard. He said the waves came up to the top of the dunes at South Beach during high tide, and included "good-size rollers.
"It overwhelmed the beach," he said. "It reformed the beach. It's not destroyed a lot, but it's going to reshape the beach."
The storm delayed or halted ferry services from New York to Maine, and kept many beaches closed.
In Montauk, N.Y., swimmers weren't allowed in the water, but surfers were out riding the waves. State parks spokesman George Gorman said almost 2,000 surfers showed up at Montauk on Sunday - the most ever counted there. They enjoyed waves that reached as high as 16 feet.
Associated Press Writers Jennifer Kay in Miami; Pat Eaton-Robb in Hartford; Bruce Shipkowski in Trenton, N.J.; Clarke Canfield in Portland, Maine; and Rob Gillies in Toronto contributed to this report.