“I think most people associate the historic immigrant experience first with Ellis Island,” said David Favaloro, a curator at the Tenement Museum on the Lower East Side, “and then specifically with this neighborhood.” The museum occupies a building at 97 Orchard Street, a five-floor walk-up that was home to some 7,000 immigrants (of mostly German and Irish descent) from 1863 to 1935, when it lost its residential designation amid a modernization of the city’s anarchic fire codes.

“The street-side area had always held some type of business, even after 1935,” Mr. Favaloro said. “It was a German-run saloon when people still lived there, and it became a kosher butcher, then an auction house, and a stove repair shop and eventually Sidney’s, a clothing store, up until 1980. But every other floor had been untouched for 50 years.”

It was this derelict edifice that the historian and social activist Ruth Abram discovered with her colleague Anita Jacobson in 1988, when they were looking for a home for an institution to memorialize the city’s immigrant past. The Tenement Museum took sole possession of the building and has been renovating these virtually untouched time-capsule domiciles ever since.

Each apartment included a “tuberculosis window” between interior rooms to provide healthful cross-ventilation in the absence of a real one, and might occupy an area as small as 325 square feet, housing, improbably, as many as a dozen people. Most rooms have now been restored to reflect the décor and living conditions experienced by the families crowded within these walls.