Hundreds begin to gather at Civic Center Plaza before the start of the annual Walk for Life anti-abortion march in San Francisco, Calif. Saturday, Jan. 27, 2018.
Hundreds begin to gather at Civic Center Plaza before the start of the annual Walk for Life anti-abortion march in San Francisco, Calif. Saturday, Jan. 27, 2018.
Photo: Jessica Christian
People gather underneath a large banner before the start of the annual Walk for Life anti-abortion march in San Francisco, Calif. Saturday, Jan. 27, 2018.
People gather underneath a large banner before the start of the annual Walk for Life anti-abortion march in San Francisco, Calif. Saturday, Jan. 27, 2018.
Photo: Jessica Christian
Carolina Martin of Modesto carries a sign up the Civic Center Bart escalator on her way to the annual Walk for Life pro-life March in San Francisco, Calif. Saturday, Jan. 27, 2018.
Carolina Martin of Modesto carries a sign up the Civic Center Bart escalator on her way to the annual Walk for Life pro-life March in San Francisco, Calif. Saturday, Jan. 27, 2018.
Photo: Jessica Christian
Robert C. Newman II carries a balloon while attending the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Robert C. Newman II carries a balloon while attending the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Carolina Martin of Modesto carries a sign while exiting Civic Center Bart Station before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Carolina Martin of Modesto carries a sign while exiting Civic Center Bart Station before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Alfredo Sanchez plays guitar while supporters around him join in song before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Alfredo Sanchez plays guitar while supporters around him join in song before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Oliva Mu�oz, left, and Maria Esquivel, second left, of Salinas greet one another while Benjamin Escalona, right, of Salinas carries a statue of Jesus Christ on the cross while attending the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif. less
Oliva Mu�oz, left, and Maria Esquivel, second left, of Salinas greet one another while Benjamin Escalona, right, of Salinas carries a statue of Jesus Christ on the cross while attending the Walk for Life ... more
Photo: Jessica Christian, The Chronicle
People walk past a large banner before the start of the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
People walk past a large banner before the start of the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Dozens climb on top of a play structure while carrying signs before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Dozens climb on top of a play structure while carrying signs before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Yellow balloons that read "Life" float above the crowd before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Yellow balloons that read "Life" float above the crowd before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Dozens climb on top of a play structure while carrying signs before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Dozens climb on top of a play structure while carrying signs before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
(From left) Michael Rex, Maureen Naylor and Charles Short with Society of St. Pius X of Los Gatos prepare an alter before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif. less
(From left) Michael Rex, Maureen Naylor and Charles Short with Society of St. Pius X of Los Gatos prepare an alter before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center ... more
Photo: Jessica Christian, The Chronicle
People browse merchandise for sale during the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
People browse merchandise for sale during the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Hundreds gather for the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Hundreds gather for the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Andrea Weever of San Francisco, center, joins other counter protesters on the outskirts of the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Andrea Weever of San Francisco, center, joins other counter protesters on the outskirts of the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
People walk past a line of tour buses before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
People walk past a line of tour buses before the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
Thousands gather for the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Thousands gather for the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
People line up along the front barricade while carrying signs during the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
People line up along the front barricade while carrying signs during the Walk for Life anti-abortion rally and march Saturday, Jan. 27, 2018 at Civic Center Plaza in San Francisco, Calif.
Photo: Jessica Christian, The Chronicle
It’s been 45 years since a landmark Supreme Court ruling legalized abortion nationwide. In San Francisco Saturday, thousands of demonstrators were set to rally and march in protest of that decision.
Every year, activists with Walk for Life West Coast plan their march for the weekend closest to the Jan. 22 anniversary of the U.S. Supreme Court’s 1973 Roe vs. Wade ruling.
The goal, according to Walk For Life’s website, is “to reach out to women harmed by abortion” and “to inform society of the damage done to women by abortion.”
A large crowd converged at the San Francisco Civic Center to look at info booths and listen to speakers before the 12:30 p.m. walk down Market Street to the Ferry Building.
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The event comes a week after President Trump addressed thousands of pro-life activists at the annual March for Life in Washington, D.C.
Market Street is expected to be closed to traffic from 10th Street to the Embarcadero from 1 p.m. until 6 p.m. and Mission Street will be closed to all but transit traffic during those same hours.
Jenna Lyons is a San Francisco Chronicle staff writer. Email: jlyons@sfchronicle.com Twitter: @JennaJourno