The Whittenton Pond Dam, a crib of crisscrossed logs that holds back the Mill River, helped make this faded manufacturing town what it was. Built 173 years ago, it provided water power to Taunton through an era when there was a mill in every neighborhood and immigrants streamed from Italy, Portugal and Poland to fill them.

Now, with the river high, the dam's rotted wooden beams shuddering and the town green silent and evacuated, many here wonder if the water is about to destroy what it helped create.

"If the dam were to break," Mayor Robert G. Nunes warned at a news conference Tuesday in his city's near-empty downtown, "we will see rising floodwaters in downtown Taunton."

For three days, officials have anxiously watched the 12-foot-high dam, which sits just upstream of Taunton's riverside downtown. They said that, after nine days of rainy weather built up excess water behind it, the dam is creaking, vibrating and allowing water to seep both through and underneath it.

"It's coming out in a lot of places it really shouldn't be," said Peter Judge, a spokesman for the Massachusetts Emergency Management Agency.

All of those symptoms seem to indicate that the dam may be on the verge of total failure, officials say. In one worst-case scenario, the dam's collapse might also cause another dam farther upstream to fail, by suddenly draining away the water on the other dam's downstream side and reducing the pressure on one side of its wall.

Officials believe the worst-case scenario in all this might be a devastating wave of water six to eight feet high, sweeping through about 100 homes near the river and Taunton's downtown commercial district.

"What the damage or impact, nobody is even guessing," Judge said.

Fearing the worst, officials in this town of about 56,000 have closed schools, asked downtown businesses to close and asked 2,000 residents to evacuate. About 90 of them went to the gym at Taunton High School, where the American Red Cross had set up a temporary shelter.

Officials said Tuesday they still had not figured out a safe way to shore up the dam.

"I've got my fingers crossed that this thing is able to hold," Gov. Mitt Romney (R) told the Associated Press. He visited the dam Tuesday and called for a renewed emphasis on inspecting dams across the state.

The crisis in Taunton has put a renewed emphasis on mill pond dams, vestiges of New England's manufacturing history that have kept holding water back long after anyone needed them for power. Massachusetts officials estimated that the structures, many privately owned, make up a large percentage of the state's 3,000 dams.

In Taunton, the Whittenton Pond Dam was part of a series that helped make its river a center of textile and other manufacturing. "They didn't call it the Mill River for nothing," said Charles Crowley, 51, a Taunton historian and a member of the city council for 18 years.

The town's mills began to fade in the late 1900s, Crowley said, but the dam stayed. It was pushed to the brink by a flood in 1968 but since had been partially forgotten.

"I didn't even know they had a dam in Taunton," said Scott Weyant, 38, the owner of a martial-arts school on Main Street. He said officials had recently told him to expect several feet of water if the dam burst. "I don't have flood insurance. Never thought I'd need it."

State officials said that a 2003 inspection of the dam revealed the need for repairs, but did not have details about what the repairs were or whether they were completed. Attempts to reach the dam's owner, a private company that purchased it just months ago, were not successful.

On Tuesday, town officials said they had some good news: The water levels in Lake Sabbatia, behind the dam, seemed to be dropping. But they said there was rain in the forecast, so no one was willing to predict when the all-clear might be given.

"It could go on for days," Nunes said.

Researcher Don Pohlman contributed to this report.

The 173-year-old Whittenton Pond Dam continued to hold yesterday despite springing a few leaks. If it fails, it could send a wave six to eight feet high through downtown Taunton.

Nathan O'Keefe, 15, left, Joseph Re, 14, and William Vu, 15, carry swimming and flotation gear in Taunton, Mass. They said they are ready if the Whittenton Pond Dam breaks.