The tower, which opened on Oct. 8, 1933, was funded by Lillie Hitchcock Coit, who left a third of her estate to build the structure.
Susie Coit Williams, Coit's cousin, was at the iconic site for Tuesday's celebration.
Williams, who now lives in Texas, said she visits Coit Tower at least once a year and has done so since she was a child.
Her father, who has since passed away, was in the U.S. Navy and emphasized the family's value of public service, she said.
"I'm so honored and so in awe," she said. "As long as I can keep coming here I will."
San Francisco firefighter Peter Arnautoff, grandson of Coit Tower muralist Victor Arnautoff, reflected on the tower's landmark birthday.
"It's so special to be able to have this family connection that has so much meaning to San Francisco and the Fire Department," he said.
Coit had been a well-known volunteer firefighter in the city despite her gender in the late 1800s and early 1900s.
The elder Arnautoff created a mural titled, "City Life," which depicts a bustling urban scene, located on the east side of the tower.
While Coit Tower is a great lookout point, Peter Arnautoff jokingly noted that the trees surrounding the landmark could use some trimming.
A birthday party and art show for the tower is scheduled Tuesday night at the North Beach venue Live Worms Art Gallery at 6 p.m.
Work by the original Coit Tower muralist and art inspired by the landmark will be on display.