One aspect of the Portland protests getting a lot of attention has been the "wall of moms" opposing federal law enforcement. They are part of a long history of mothers leading activism.

STEVE INSKEEP, HOST:

Protests against police brutality in Portland, Ore., include a special feature. Along with the demonstrators in masks and the clouds of tear gas and the police in riot gear, Portland has lines of women, arms linked, standing in front of the crowd. They're known as the wall of moms. NPR's Danielle Kurtzleben found there is a history of moms as the face of protest.

DANIELLE KURTZLEBEN, BYLINE: Candace Lightner became an activist 40 years ago, after her daughter was killed. By now, she says, telling the story doesn't sting the way it used to.

CANDACE LIGHTNER: It's not difficult at all because I've done it so many times. So it's all right. So Carrie was killed on May 3. And it was a hit and run, and I learned that he was a multiple repeat offender drunk driver.

KURTZLEBEN: And so just four days later, she started putting together a new group - Mothers Against Drunk Driving, or MADD. At the time, she was grieving, so she wasn't really thinking about what kind of power moms specifically might have.

LIGHTNER: You know, the press used to call us motherhood, God and apple pie. And it just sort of rang, and I just think that wouldn't have happened if it had been predominantly men. I just don't.

KURTZLEBEN: Today there's Moms Demand Action, which advocates for gun control. The mothers of the movement are women whose Black children have been killed by police or gun violence. Many such groups are started by women like Lightner, who lost children tragically. That fuels their activism. But motherhood also is a part of why people pay attention, says Katrina Bell McDonald, retired professor of sociology at Johns Hopkins University. She spoke to NPR via Skype.

KATRINA BELL MCDONALD: There's the one image of the mother at home, very quiet and taking care of her business. And then there's the woman who gets mad because her child is threatened. And that's, I think, why people are so interested when they see mothers banding together. It's as if they've gotten to a point where they've come out of the house. They're pissed.

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KURTZLEBEN: White moms are often given more of a voice than Black moms, says Dani McClain, author of "We Live For The We: The Political Power Of Black Motherhood." She also spoke via Skype.

DANI MCCLAIN: It's often been the case that white women are seen as, you know, good mom, whereas Black moms have often been - our motherhood is questioned. It's like, are we good moms? Do we have enough money? Are we married?

KURTZLEBEN: She adds that simply looking out for their families pushes many Black moms into activism.

MCCLAIN: One thing to remember when it comes to Black mothers is that advocacy and activism has always been a part of our role in families.