Several people rotated shifts so a small group at a time could hold a candlelight vigil outside the Bexar County Magistrate's office throughout the night and into Wednesday morning.
They waited until all eight people arrested Tuesday outside the old Univision station on Cesar Chavez were released.
Demolition started again on Tuesday afternoon when a judge sided with the developer, allowing the tear-down to continue.
Five were arrested for trespassing. Four of them tried to get in the way of the demolition equipment. Three others were arrested for laying on the sidewalk to stop a water truck from getting in.
"The city of San Antonio needs to know what's going on as far as the way people are getting treated, and the way historical buildings and sites in San Antonio are trying to be saved. So I think it's a very good thing that we were definitely heard and seen," said Patrick Pineda, who was arrested for trespassing.
Even after a night in custody, the protesters said it was worth it.
"That building belongs to the community. It is part of San Antonio's legacy and part of our history, and it's up to any and all of us to put our bodies on the line to protect that heritage," said Jessica Guerrero, who was arrested for blocking a passageway.
More than half of the main building on the site was torn down, but the group said they would continue to check in on the developer, Greystar, to make sure it was following environmental guidelines for demolition.
"Just like they ask us to abide by the rules, we're asking them to abide by the rules," said Susan Segura, who waited overnight for others to be released from the magistrate's office.
She said there was a break-down in the city's process for designating and saving historic buildings.
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