One of the fastest-growing neighborhoods in New York City in the last decade, the Lower East Side, is being grouped among the most “endangered” historic places in America.

The National Trust for Historic Preservation yesterday said the Lower East Side is one of 11 architectural, cultural, and natural heritage sites that are most at risk “for destruction or irreparable damage.”

“New hotels and condominium towers are being erected across the area, looming large over the original tenement streetscape. As this building trend shows no sign of abating, it threatens to erode the fabric of the community and wipe away the collective memory of generations of immigrant families,” the group said in a statement.

The 2008 list of endangered sites includes California’s state park system, the Boyd Theater in Philadelphia, the Great Falls Portage of Montana, and the Bonnet House Museum and Gardens in Fort Lauderdale, Fla.

The idea that the neighborhood is “endangered” is a surprise to a number of residents, professors, and business owners who say the area is booming with new developments, retail stores, restaurants, and art galleries. New condominiums are selling for more than $1,200 a square foot — a price that is comparable to apartments in neighborhoods such as the Upper East Side, Greenwich Village, and TriBeCa.

“It is one of the most vibrant and dynamic parts of New York City today,” a professor of urban policy and planning at New York University, Mitchell Moss, said yesterday, expressing surprise when told of the designation.

Mr. Moss said the Lower East Side has been changing ever since the first people settled there, and has always shown a great capacity to absorb new types of New Yorkers and to change. “The overall neighborhood is witnessing a transformation. And just as young people move into that area, I certainly hope they are not planning to bring back historically dangerous conditions like cholera, typhoid, and open sewers,” he said.

Much of the area’s recent development has followed a precipitous drop in crime. In the 1980s and 1990s, much of the neighborhood was plagued with drug abuse and violence.

In the two major police precincts that make up the Lower East Side, the fifth and the seventh, violent crime dropped 76% and 69%, respectively, between 1990 and 2007, according to NYPD statistics.

The “endangered” designation comes just as the city is planning a 110-block rezoning of the East Village and the Lower East Side that would, for the first time, establish height limits for parts of the low-rise neighborhoods but also allow for residential development along a number of the area’s wider avenues. For some residents and preservationists, the proposed rezoning does not go far enough to curb development. They are seeking a historic district designation by the Landmarks Preservation Commission.

The executive vice president of the Lower East Side Tenement Museum, Renee Epps, defended the “endangered” designation. “It needed some national attention, and this seemed like a great way to do that,” she said.

Ms. Epps said the Lower East Side Tenement Museum was one of several organizations that helped lobby for the designation, and the organization is advocating for a historic district.

“Throughout the city, we are seeing huge developments and haphazard renovation jobs to the tenements, and we are losing historic fabric even if we are not losing the buildings,” Ms. Epps said.

The director of marketing for the Lower East Side business improvement district, Noelle Frieson, suggested that the National Trust for Historic Preservation may have gone too far. “I personally don’t feel as though it is endangered because the people who live here and work here are very pro-Lower East Side. They love the history and they love the character and that is why they moved down here and they look to preserve those things,” she said.

“Right now, we are just trying to get people down here during the day to show people that we are a neighborhood of entrepreneurs and we have historically been a neighborhood of entrepreneurs,” Ms. Frieson said.

A broker for Prudential Douglas Elliman, Andrew Landsman, said he focuses 85% of his work in the Lower East Side, and he said business is booming.

“I have never been busier and never made more money,” he said.

Mr. Landsman is also a resident, and said he has taken issue with a number of recent developments that have sprouted up near his apartment building — even though he happens to live on Norfolk Street near Delancey in a tall, glass condominium known as “Blue” that some have criticized as uncharacteristic of the neighborhood.

“We do think it is under siege by a lack of respect for the local culture and aesthetics in general,” Mr. Landsman said.