Family continues decades-long tradition of Stern Grove's free summer concerts

They arrive from all corners of San Francisco and beyond. Some with baby strollers, others with their four-legged friends leading the way.

Within minutes, every inch of this urban oasis has been claimed.

"It's really a special place," said Jason Goldman.

Along with his identical twin Matthew, Jason is one of the fifth-generation custodians of Stern Grove -- the home of an annual outdoor music festival that's become an institution in this neck of the woods.

"There's nothing better than a concert where everyone is smiling, having fun, all coming together for the sake of community," said Matthew Goldman.

In 1931 their great-great grandmother, Rosalie Meyer Stern, gifted 33 acres of land to the city of San Francisco in her husband's memory.

Her husband, Sigmund Stern, was the nephew of Levi Strauss, the man behind the famed brand of jeans.

For the last 87 years, her descendants have been hosting a summer-long music festival every year.

Douglas Goldman, Jason and Matthew's dad, ran the festival for nearly a quarter of a century. He said the idea was to bring joy to San Francisco during the Great Depression. Which is why one of Stern Grove's founding principles is that the concerts be 100% free.

"You had musicians who were out of work during the summer, so that was part of the equation. It gave them an opportunity to work," he said.

What started with classical music and opera now hosts some of the biggest names in pop, rock and EDM. Over the years, its seen the likes of Buddy Guy, Phil Lesh, the Isley Brothers, Lyle Lovett, the Revolution, Os Mutantes and the Indigo Girls.

These days the Goldman twins are focused on appealing to younger audiences, bringing in acts like electronic duo Bob Moses and indie pop duo Tegan and Sara.

Now they hope Stern Grove lasts another 87 years and that, like their family's timeless jeans, it never goes out of style.

"If the Earth is still here, Stern Grove will still be here," Jason Goldman said.