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Many thousands of anti-abortion protesters from across California marched through downtown San Francisco on Saturday, calling for restrictions on a medical procedure that was legalized more than 40 years ago.

A massive and diverse crowd of protesters rallied in front of City Hall before marching down Market Street to Justin Herman Plaza for the 10th annual "Walk for Life West Coast." They chanted "Pro Life" and carried signs that read "Defend Life" and "Women deserve better than abortion."

On Wednesday, thousands of abortion protesters participated in the annual Walk for Life rally in Washington, D.C. to mark the anniversary of Roe v. Wade, the 1973 Supreme Court ruling that legalized the procedure.

San Francisco police did not immediately provide an official crowd estimate, but at one point marchers stretched across more than a mile of Market Street, the liberal city's main thoroughfare.

High school senior Nancy Castellanos came to San Francisco on one of six buses of worshippers from St. Peter's Catholic Church in Dixon, about 70 miles away. She believes the laws need to change to make it harder to get an abortion.

"I am 100 percent, completely against abortion," Castellanos, 17, said. "If you don't want the child, there's always adoption."

John Paine, 52, arrived with people from his church group in Visalia in California's Central Valley, after making a 3 1/2-hour drive to San Francisco on Saturday.

"I'm ashamed that my country sanctions the killing of the most defenseless of its citizens," Paine said. "Human life in all its stages is sacred and should be protected."

A small group of pro-abortion rights activists protested the march on Market Street, holding signs that read "Abortion on demand and without apology."

Anna Wilson, 20, a commercial artist who lives in San Francisco, said she participated in the Walk for Life march two years ago, but said she's since changed her stance on abortion.

"I realized I was looking at it in a real childish way," Wilson said. "I'm not pro-abortion. Nobody's pro-abortion. But I am pro-choice. I think that women should have every single choice available to them, as much as men do."

Supervisor David Campos introduced a resolution last week opposing the dozens of "Abortion Hurts Women" banners that organizers hung from street lamps on Market Street. The resolution says "the prominent display of false anti-abortion statements on public property on Market Street misrepresents the City's support for reproductive health, rights and justice."

Over the last several decades, anti-abortion groups have focused on placing relatively small restrictions on abortion, especially in conservative states with Republican-dominated legislatures. But lawmakers in those states are under increasing pressure from activists to take stronger action to limit abortion.

But California, which has a Democratic governor and Legislature, expanded abortion access last year with a measure that allows nurse practitioners, certified nurse midwives and physician assistants to perform a type of early abortion.