Every summer thousands come to the Eldridge Street Synagogue in New York’s Lower East Side for the annual Egg Rolls and Egg Creams Festival.

The synagogue, dating back to 1887, was the first built in the district by Jewish immigrants from East Europe in search of a better life. And although their descendants have largely left for more prosperous pastures in the suburbs, the festival celebrates the culture they brought with them, as well as that of the Chinese community who have more recently settled in the neighbourhood.

By the earlier 1980s, the synagogue had become dilapidated. It was as though it were “held up by strings from heaven,” said Roberta Brandes Gratz, who launched a project to restore it. In 2007 it opened as a museum, dedicated to remembrance of the past.

But it is far from an isolated heritage site, explains San Francisco State University academic Rachel B. Gross. In her recent book, Beyond the Synagogue, she argues that it reflects a wider trend among American Jewry, to keep alive the memories of their immigrant roots. “American Jews… engage in the ostensibly non-religious activities of Jewish genealogical research, attending Jewish historic sites, consuming markedly Jewish food and purchasing books and toys that teach Jewish heritage to their children.”

She refers to “ostensibly non-religious” activities because in her view they are actually a form of “lived religion”. Typically we associate religion with prayer and ritual in places of worship. But she prefers a broader definition, which is “best understood as meaningful relationships and the practices, narratives and emotions that create and support these relationships”. Nostalgia becomes, she says, “a mitzvah”, that binds the living to those who came before.

For example, a colouring book for children which is sold at Eldridge Street tells the story of a little girl whose family emigrated in the early 20th century. “Each week, when we stepped through the door [of the synagogue], our dark tenement seemed far away. Inside we found light and space and peace.” Through this lens, those who rarely set foot in a synagogue today can experience it as a communal haven, a place of tranquillity.

Social scientists have often spoken of the “civil religion” that developed in the USA post-War, centred on memorialisation of the Holocaust and support for the state of Israel. The nostalgic engagement with the Ashkenazi past offers “a communal narrative that can be more cheerful than remembrance of the Holocaust and less communally divisive than Israeli politics,” Gross argues, and one which may complement rather than replace the other two.

Moreover, the Jewish story is an optimistic one, confirming America’s faith in progress as the children and grandchildren of those who disembarked at Ellis Island integrate into the land of opportunity.

But this retrospective view acknowledges some of the sacrifices of the past — a nostalgia that “recognises that changes and improvements have come at a cost, mourns that which has been lost, and retrieves select stories and values as useful for the present”.

She quotes Aaron Mandell, the member of a chavurah group which meets monthly for services in another historic building, the Vilna Shul in Boston, which opened in 1919 and might have been sold for a parking lot many years later had the prospective buyer not been arrested in a drugs bust. “When you come in here, you immediately feel like you’re part of Jewish history. I think it’s a way to connect to Judaism that’s very tangible,” Mandell told her.

Others find their connection with history through researching their family tree. Jewish genealogy began to take off in the 1970s. “Each time I have uncovered the name of one of my long-forgotten ancestors, I have been filled with the mystical feeling that I was indeed rescuing that ancestor, not from hellfire perhaps, but from oblivion,” said Dan Rottenberg, author of the first Jewish genealogical manual in 1977, Finding Our Fathers: A Guidebook to Jewish Genealogy. (His comment on hellfire alludes to the Mormon practice of posthumous baptism to secure salvation for departed ancestors).

In the Jewish genealogical journal Avotaynu (“Our Fathers”), Rabbi Ben-Zion Sandman described the pursuit as “a spiritual journal into the lives of those who made us what we are”.

For relatives murdered in the Holocaust, a place on the family tree can be a substitute for a grave.

The Ashkenazi immigrant experience is transmitted to children through a growing literature, with books such as Eric Kimmel’s When Mindy Saved Hannukah or Sheldon Oberman’s The Always Prayer Shawl, inspired by the author’s coming across his zeida’s tallit when his son was preparing for his bar mitzvah. “The tallit exists in the story not as a symbol for religious law and ritual, but as a talisman of familial continuity,” she explains.

These and other tales have been widely distributed by the children’s book club, P J Library, which she says, is “one of the most influential Jewish organisations in North America”.

Finally, there is the Ashkenazi food revival, with a new wave of restaurateurs and deli-owners offering reinventions of heimishe dishes. Traditional Jewish food rap, which came to be associated with bottled gefilte fish and packeted chicken soup, “got a bad rap,” observed Mitchell Davis, author of The Mensch Chef: Or why delicious Jewish food Isn’t an oxymoron.

Instead enterprises like the Gefilteria in Brooklyn have recreated old dishes for more sophisticated palates. For Gross, “American Jewish foodways provide individuals with a sense of community and belonging across time and space.”

Whereas commentators often view American Jewry — Orthodoxy apart — as in the grip of religious decline, she suggests the picture is more complex and sees change rather than erosion. You may not be convinced by her characterisation of all this as the practice of “religion” rather than of ethnic culture. But memory is an important part of Jewish tradition and she reminds us there are many different ways to access Jewish heritage — to be encouraged and embraced.

Beyond the Synagogue: Jewish Nostalgia as Religious Practice, Rachel B.Gross is published by New York University Press, £31