Twitter co-founder Ev Williams to step down from the company’s board

“I’m very lucky to have served on the @Twitter board for 12 years (ever since there was a board),” he wrote. “It’s been overwhelmingly interesting, educational—and, at times, challenging… Thank you, @jack and @biz for starting this crazy company with me—and continuing to make it better and better. And to my fellow board members, new and old—some of the most thoughtful people I’ve ever known.”

Williams, the founder and CEO of online publishing platform Medium and co-founder and partner at Obvious Ventures, served as Twitter’s chief executive from 2008 to 2010 following Jack Dorsey’s, Twitter’s current CEO, original stint as CEO. Williams was succeeded by Dick Costolo, who after a five-year stint at the helm, relinquished the throne back to Dorsey.

Twitter’s board of directors includes Bret Taylor, president and chief product officer at Salesforce; Debra Lee, president and CEO of BET Networks; and executive chairman Omid Kordestani.

Twitter’s stock closed up 3 percent Friday, trading at nearly $32 a piece for a market cap of north of $24 billion.