Craigslist founder signs the Giving Pledge, and his fortune will go to military families, fighting cyberattacks—and a pigeon rescue

Of the wealthiest people in the world, about 250 have pledged to give away the majority of their fortune—an effort coined the Giving Pledge. It was started by Bill Gates, Melinda French Gates, and Warren Buffett in 2010, and billionaires including Mark Zuckerberg, Elon Musk, Larry Ellison, and Bill Ackman have signed on. 

Although it’s often also referred to as the Billionaire’s Pledge, other wealthy donors have committed to the endeavor. One of the latest signatories is Craigslist founder Craig Newmark, who announced on LinkedIn this weekend he’s officially joining the Giving Pledge.

“Okay, I’ve formally signed up for the Giving Pledge, sometimes considered the Billionaire’s Pledge, though I’ve never been a billionaire, particularly after I gave away all my Craigslist equity to my charitable foundation,” Newmark wrote. “Seems like a good way to officially enter my middle seventies, which I’ve done today.”

Newark built his fortune by founding popular online marketplace Craiglist in 1995. It started as an email list for local San Francisco residents but turned into an online classifieds page the following year. Today, Craigslist is estimated to be worth...