Today, South of Market, a wedge-shaped neighborhood in northwest San Francisco, is home to tech giants such as Twitter and Airbnb, but for most of its existence it was a very different kind of place.

Once famous for its “factories, slums, laundries, machine shops, boiler works, and the abodes of the working class,” as writer Jack London noted in 1909, it changed dramatically in the 1960s when many businesses that called the district home moved out and a community of artists and gay men and women emerged in its place. In the late 1970s, in the face of then expanding dereliction and as part of efforts to remake the neighborhood, city authorities condemned many of the residential hotels that had become a hallmark of the area, displacing many residents and small businesses.

It was at this time that photographer Janet Delaney moved to the area, seeking cheap rent. Between 1978 and 1986 she captured a neighborhood at the cusp of change. One that was not salubrious — she was held up at knifepoint and had her camera stolen — but one where behind the rough edges, a small but strong community of families and businesses still thrived.

“In my first two years of college I spent a lot of time, like many people in the early 70s, thinking of formal issues, like structure, and how a photograph is constructed,” Delaney says, recalling the kind of aesthetically-driven photography she was making up until she moved to the area. ” [I was] responding to minimalism, and how photography addresses these concepts.”

Later, a six-month solo trip to conflict-riddled parts of Central America left a deep impression on Delaney, and saw her take a socially-conscious turn with her work. Upon returning, the often-tough lives of her neighbors seemed to take on a new significance and she felt the need to document them. Using a large 4×5 view tripod-mounted camera, she made portraits and architectural views and shot the interiors of local businesses, in an attempt to document life in the neighborhood.

The images that emerged are as frank as they are beautiful and are a testament to a once gritty, even vibrant neighborhood. Indeed, they bear an uncanny resemblance to pre-war documentary photography. It is perhaps all down to the camera, Delaney says: a bulky contraption that takes up a large amount of space but yields finely detailed images. And for the photographer, the ever obvious camera itself became an important part of the documentation process.

“The camera gave a sense of honor to a neighborhood that nobody ever considered, a neighborhood the city felt it could demolish,” Delaney says.

By 1988, with rents getting ever higher, Delaney, now a mother, moved across the bay to Berkeley. “I wouldn’t have left if that rent hadn’t been so high,” she adds, feeling that she was pushed out of her old neighborhood by rising prices. And that process doesn’t seem to be slowing as the neighborhood, now known as SoMa, continues to gentrify.

“I’ve continued to photograph South of Market,” Delaney says. “There’s more of a bustle, there’s more going on. But it’s really expensive. People are moving into high rises. It’s a more elegant, beautiful, [but] slightly alienating environment.”

Janet Delaney: South of Market runs until July 19, 2015 at the De Young Museum in San Francisco

Myles Little is an Associate Photo Editor for TIME

LIFE in a Great City: San Francisco