"When we first started coming here, there were no kids outside," Richie told People magazine. "To see the place come to life and have a place to come outside and be kids, and have their imaginations run wild, it's really awesome."
Richie and Madden's 2-year-old daughter Harlow was on hand for the ceremony. As was Madden's twin brother Benji Madden.
This is the most recent project the stars have been working on through the Richie-Madden Children's Foundation.
The new playground will serve hundreds of low-income children.