How old does something have to be to be considered “historic?”

Index Tribune courtesy of the Sonoma Valley Historical Society
The modern commercial building, with housing in back, was built in 1960 by real estate agent W. A. McFarlane. McFarlane practiced his profession through the 1960s, possibly at other locations. He died in 1975.
The gap in this story is a long one; between the 1960s and 2000, when Nola Lum Hsu filed her Fictitious Business Name statement for the Golden Garden Restaurant. It’s also during this period that the brick-faced addition appeared.
Thailand Thai took over from Golden Garden in 2008.
The building was vacant in 2010 but Norm Owens was getting ready to open his Hot Box Grill that year.
According to Sonoma Magazine
Former Cafe La Haye chef Norman Owens has opened Hot Box Grill in Sonoma — technically Boyes Hot Springs — in what’s fast becoming a gourmet gulch. The Aqua (SF) and Canlis (Seattle) alum garnered serious cred while in the Sonoma kitchen before leaving.
Chef Rob Larman opened Cochan Volant in 2016, complete with the flying pig sculpture by Brian Tedrick, on the roof. In 2020, it continues to pump out fragrances that stimulate the salivary glands.
Please comment if you can fill in the gaps in the story of this building.
Hot Box Grill photo courtesy of Sonoma Magazine.