When Laurie Tobias Cohen was a young girl in New Jersey, her family often visited the Lower East Side on Sunday afternoons to shop for clothing and tableware on bustling Orchard Street. Afterward, she recalls, crowds would flock to the 1,200-seat Orthodox synagogue Beth Hamedrash Hagadol to hear lectures by the rabbi, Ephraim Oshry, a world-renowned scholar.

“It was so packed, they’d sit in the stairwell to hear him,” Ms. Cohen, who is executive director of the Lower East Side Jewish Conservancy, said.

A few blocks away, Beth Hamedrash Hagadol, one of the first synagogues founded in New York City by Eastern European immigrants and among the oldest congregations in America, now sits padlocked and empty, with bits of plaster falling from the blue-painted, arched ceiling, and gaping holes in the rain-damaged roof.

The Lower East Side, the area between Canal and Houston streets and Broadway and the East River, is at a crossroads. As interest in historic areas and “heritage tourism” reaches a fever pitch, the neighborhood has seen some of its iconic tenement buildings — which housed waves of Jewish immigrants fleeing Eastern European pogroms in the late 19th and early 20th centuries — give way to chic restaurants and bars. There has also been an influx of high-end development, including Blue, a 16-story pixilated high-rise condominium on Norfolk Street, and Thompson LES, a new boutique hotel by the Pomeranc Group that is slated to open at 190 Allen St. next week.

Preservationists are hoping to help shape the changing face of the area. The National Trust for Historic Preservation called the Lower East Side one of America’s 11 Most Endangered Historic Places earlier this year, and the president of Manhattan, Scott Stringer, is reviewing a rezoning proposal to set height limits in the neighborhood. The city’s Landmarks Preservation Commission is currently reviewing the results of a survey it conducted of more than 2,300 buildings on the Lower East Side to determine which buildings could be included in a historic district or receive individual landmark status.

It’s within this maelstrom that the Lower East Side Conservancy has undertaken the difficult task of renovating Beth Hamedrash Hagadol, built in 1850 and situated just a block south of the new Blue high-rise. Ms. Cohen’s group is vowing to restore the crumbling structure, which engineers have deemed unsafe for use by its dwindling congregation, and transform it into a visitors center with educational programs and gallery space.

Several weeks ago, the group secured a promise of $215,000 in funding from the Lower Manhattan Development Corporation, and was granted $215,000 from the federal Department of Education four months ago. The group was also promised a combined $980,000 from New York State, the City Council, Mayor Bloomberg, and the Manhattan Borough President’s office several years ago, though the bulk of the city funds are still making their way through the city’s contracting process.

The Conservancy is hoping the grants it has received will jump-start its fund-raising efforts for the $4.5 million renovation. “We’re starting to gain traction,” the executive director of the United Jewish Council of the East Side, Joel Kaplan, said, adding that the group will seek to raise $400,000 in private funds for the first phase of construction, which will secure the structure and roof.

Conservancy members said they hope the renewed interest in cultural tourism will assist in the daunting task of raising the funds for Beth Hamedrash Hagadol. “Heritage tourism has exploded in the past 10 years,” Ms. Cohen said. “There’s an increasing thirst for the opportunity to visit places that are hallmarks of heritage — this fits into that.”

Development on the Lower East Side has increasingly become a source of concern for preservationists. “It’s really the seminal neighborhood for the U.S. Jewish community,” the northeast regional director of the National Trust for Historic Preservation, Wendy Nicholas, said of the Lower East Side. “Modern high-rise condo buildings are popping up in the middle of otherwise intact late-18th-century blocks. If that trend continues, we’re very concerned that the whole historic neighborhood will be unrecognizable.”

In May, the Department of City Planning began the public review process for its proposal to rezone over 110 blocks in the East Village and Lower East Side, seeking to establish contextual zoning districts with height limits. The proposal is scheduled for a public hearing with the city planning commission August 13.

Not everyone is pleased with the plans. On Tuesday, a crowd of demonstrators gathered in front of 1 Centre St. to protest the rezoning plan, presenting borough president Scott Stringer with a 10,000-signature petition asking that the proposal be replaced with one that includes more low-income housing.

Opponents of the proposed historic district say it may inhibit the area’s traditional entrepreneurial spirit. “It can hurt businesses if it’s not looked at very carefully,” the executive director of the Lower East Side Business Improvement District, Roberto Ragone, said.

The proposed Beth Hamedrash Hagadol renovation, too, is an uphill battle. The building is one of the largest synagogues on the Lower East Side, making it a gargantuan undertaking for the Lower East Side Conservancy, which for the past decade has helped local congregations raise millions of dollars for synagogue restoration, Mr. Kaplan said.

Moreover, the group has faced skepticism about the need for restoring the building because there are many other synagogues operating on the Lower East Side. “You don’t need another 1,200-seat synagogue,” Mr. Kaplan said.

Still, the group remains committed to preserving the historically significant building. In its heyday, the congregation’s rabbi was Jacob Joseph, the first and only chief rabbi of New York City, while the synagogue served as “the nerve point for all of New York,” open 22 hours a day and receiving thousands of charity appeals, the congregation’s rabbi, Mendel Greenbaum, said. The group — now with only about 20 regularly attending members — met in the basement until an engineer deemed the aged facility unsafe for use, forcing the congregation to share space with a Henry Street congregation.

“Built history is extremely important,” Ms. Cohen said. “How else do we convey to the young where they came from?”