Won’t you be my neighbor? How porch culture fights loneliness.

Lida and Mark Simpson sit on the steps of their porch with friends while the blues rock band Red Medicine plays in a yard across the street. People crowd all four corners of the intersection, dancing and chatting. It’s PorchFest in Petworth, a neighborhood of Washington, D.C. Some 100 performers will play on porches and yards throughout the day. A new group of people walks up, searching for space with a view of the band. “Sit, sit,” says Ms. Simpson with a big smile, gesturing toward the wall at the edge of the yard.

The Simpsons, who have a 4-year-old and a 6-year-old, chose Petworth because it’s walkable, close to restaurants and playgrounds and public transit, and still has a neighborhood feeling. When they first moved in eight years ago, Ms. Simpson says she hoped for an active front porch culture. But it didn’t quite coalesce