Once upon a time, four left-wing groups in New York built housing that had activism at its core. They bought land in the Bronx and, with a modest investment from each purchaser and some subsidized mortgages, built low-cost co-ops that offered social services, libraries and meeting spaces for radical political groups.

The history of these developments, the Amalgamated Houses (bordering the southern edge of Van Cortlandt Park), Sholem Aleichem Houses (on nearby Giles Place), and Farband Houses and United Workers Co-operative Colony (both in Williamsbridge), is explored in a new exhibit at the Museum of the City of New York.

Erected in the 1920s by labor unions and progressive Jewish organizations, the buildings recall a halcyon time in New York. But their history includes suffering as well. The stock market crash of 1929 caused massive upheavals in these utopian communities. By 1930, the Sholem Aleichem complex, the United Workers buildings and half of the Farband development were all in foreclosure. Ultimately, hundreds of families lost their investments and were transformed into renters again.

Today, the 1,500-apartment Amalgamated Houses and two of the four buildings of the smaller Farband development remain limited dividend co-ops, meaning they can't be sold for a profit. Edward Yaker, whose parents bought into Amalgamated in 1941 and who is now head of its board, says the development survived in part because of a strong connection with two powerful (and financially stable) unions: the Amalgamated Clothing Workers and the International Ladies Garment Workers Union (both now part of UNITE). "The banks knew the unions stood behind the co-op," he says. He also credits Abraham Kazan, who ran the Amalgamated's Credit Union and managed the co-op from 1927 to 1957.

The original Amalgamated co-operators put up $500 a room for their homes. By 1950, the purchase price had risen to $650 per room. Today's price is $3,000 per room--an increase that lags behind inflation. If they leave, residents must sell their shares back to the co-op, which then selects new purchasers from a waiting list. Carrying charges--the co-op equivalent of monthly rent--average $158 per room.

Yaker reports that the co-op has declared itself a naturally occurring retirement community to better serve its long-time residents. It is also implementing a capital assessment of about $5,000 to refurbish some kitchens and bathrooms that have not been touched since the 1920s. Still, says Yaker, expenses will stay low: "It remains affordable, the same as it's been throughout our existence."

In the Bronx, at the Museum of the City of New York is on view through March 20.