NEW YORK — Planned Parenthood’s 100th anniversary celebrations this weekend came with a sense of relief for the group that traces its roots to a time when women could not vote and contraception was illegal. The organization, whose services include birth control, sex education and abortions, has survived largely intact in the face of violence, vilification and fierce efforts in Congress and many states to cut its funding.

There’s been some adverse impact: In Texas and Wisconsin, for example, some Planned Parenthood facilities closed after the states cut off funding streams. But most of the Republican-led defunding efforts have been thwarted, and multiple investigations related to the disposition of fetal tissue have thus far failed to prove wrongdoing on Planned Parenthood’s part.

Meanwhile, the organization has received strong backing from the Democratic Party, including presidential nominee Hillary Clinton, and says support from the public is robust.

“The attacks have only strengthened our resolve,” said Planned Parenthood president Cecile Richards. “I do believe we are in a stronger place today than a year ago, or five years ago.”

Planned Parenthood’s foes, who denounce its role as the nation’s leading abortion provider, show no signs of relenting. Eleven anti-abortion groups issued a joint statement depicting the 100th anniversary as “a tragic milestone for our nation and a reminder of the millions of unborn children who will never have a birthday.”

However, opponents also express some frustration at Planned Parenthood’s lobbying and fundraising skills.

“They put themselves in role of martyr while at the same time making money hand-over-fist,” said Kristi Hamrick of Americans United for Life. “The thing they’re really good at is public relations and marketing and making money.”

Planned Parenthood dates its beginnings to Oct. 16, 1916, when Margaret Sanger, her sister and a friend opened America’s first birth control clinic in Brooklyn. It was a challenge to mores and laws of the time, four years before the 19th Amendment gave women the right to vote.

The clinic was raided, and Sanger was convicted of disseminating birth control information. Undaunted, she founded two organizations that later merged to form the Planned Parenthood Federation of America.

Sanger’s personal legacy is complicated. She opposed abortion — and yet the organization she founded now provides about one-third of America’s estimated 1 million annual abortions. Her views on eugenics and racial issues remain a subject of bitter debate to this day.

Over the decades, Planned Parenthood played pivotal roles in easing laws against contraception, popularizing the birth control pill and setting the stage for the Supreme Court’s 1973 Roe v. Wade ruling that established a woman’s right to have an abortion.

Its clinics have been repeated targets of bombings, arson and protests. Last November, a gunman killed three people and injured nine at a Planned Parenthood clinic in Colorado. The man charged with the attack said he acted because of his opposition to abortion.

Threats against the organization escalated in mid-2015 after an anti-abortion group called the Center for Medical Progress began releasing secretly recorded videos alleging that Planned Parenthood sold fetal tissue to researchers for a profit in violation of federal law.

Investigations by several states and congressional panels produced no evidence of wrongdoing, though one probe in the U.S. House remains in progress. David Daleiden, the activist who orchestrated the undercover videos, predicts that the outcome of that investigation will spell the end of Planned Parenthood’s “abortion empire.”

Planned Parenthood says affiliates in two states continue to donate fetal tissue to medical researchers; they no longer accept any reimbursement to cover the costs of these programs.

The videos rekindled long-running efforts to cut off Planned Parenthood’s federal funding, which accounts for about one-third of its annual $1.3 billion budget. Republicans in Congress finally managed to get a bill to President Barack Obama that would have achieved that goal, but he vetoed it in January.

Across the country, politicians in about two-dozen states have either enacted or proposed measures targeting Planned Parenthood with defunding. In most of those states, the cuts didn’t take effect, often because of successful lawsuits filed by Planned Parenthood.

“They’re doing the smart thing by going on offense,” said anti-abortion leader Marjorie Dannenfelser of the Susan B. Anthony List. “I think there was a lot of damage done to them, but it’s a longer struggle than I would like.”

Most of the taxpayer money received by Planned Parenthood covers birth control and other medical services for low-income women. By law, federal funds may not be used directly for abortions except in rare cases, but anti-abortion activists argue that the grants, by covering operational costs, free up other money to provide abortions.

Statistics in Planned Parenthood’s annual reports show how its operations have changed over the past decade. The nationwide number of local health centers has dropped from about 850 to about 650; there’s been a decline in the number of contraceptive services provided; and the annual number of abortions performed rose from 264,943 in 2005 to 323,999 in 2014.

Cecile Richards said Planned Parenthood is pleased that more women can now obtain effective contraception on their own, without the need to visit a health center. She attributed the increase in abortions to the fact that Planned Parenthood clinics often have been able to remain open in the face of tough state regulations that forced the closure of numerous other clinics.

Looking ahead, what’s on Planned Parenthood’s agenda?

Long-term, Richards said Planned Parenthood aspires to use technology to get more information and services to clients through digital means. And she expects the client base to change, with more men and transgender people availing themselves of sexual-health services.

Short-term, Planned Parenthood is launching a yearlong program of activism and celebrations to mark the centennial. And its political action fund is deeply engaged in the election campaign, with a $30 million program that’s supporting Clinton, opposing her GOP rival Donald Trump, and targeting Republicans in key Senate races. Trump has endorsed a plank of the GOP platform that says Planned Parenthood should be denied public funding as long as it performs abortions.

If Clinton wins, Planned Parenthood’s federal funding will be secure during her term. Rep. Jan Schakowsky, an Illinois Democrat who supports abortion rights, believes the GOP campaign against the organization might lose steam as a result.

“I think there will be a winding down of these attacks and a stepping up of the counterattacks,” Schakowsky said. “With a woman in the White House, women will be feeling more empowered, insisting on control of themselves and their bodies.”