Ms. Guzmán describes leaving the neighborhood as “traumatic” and “one of the most difficult moves of my childhood.” Her family bounced from New Jersey to East New York in Brooklyn and, later, to Sunset Park in Brooklyn, “where we found some semblance of stability,” she said.

Former tenants of the razed buildings, including those who were children at the time, will be given preference for an apartment in the housing lotteries. They must provide government-issued identification as proof of residency and meet income and eligibility requirements. An informational sheet for former tenants is available on the website of Essex Crossing, which is being developed by Delancey Street Associates.

James Yolles, a spokesman for Delancey Street Associates, said in a statement that the developer is working “to develop a list of those who identify themselves as former site tenants.”

The city, however, is not trying to locate former tenants, nor will it provide housing subsidies for them should their income not meet the minimum requirement. “We are not actively seeking residents,” said Juliet Pierre-Antoine, a spokeswoman for the Department of Housing Preservation and Development. Instead, “We are going to have them come to us.”

So the task of finding people falls on the shoulders of people like Harriet Cohen, the chairwoman of the Seward Park Area Redevelopment Coalition, a community group commonly referred to as Sparc. “It feels like we’re the guardians of the site tenants,” Ms. Cohen said.

Sparc has held vigils, distributed postcards and set up a Facebook page to locate people. But 50 years is a long time and “there are a lot of José Ramírezes,” Ms. Cohen said. The group has compiled a list of some 200 former tenants.

Edward Delgado, a member of Sparc whose family was displaced from the site when he was 15, found a childhood friend from the neighborhood on Facebook. But she lives in Alaska. Now 64 and nearly blind, Mr. Delgado doesn’t live far from his old home, but he misses long-demolished shops. There was the bodega on Clinton Street where he worked as a delivery boy and met the girl who would one day become his wife. “It wasn’t like we lost our apartment,” he said. “It was like we lost our home, our community.”