In 2010, when Mark Mebus opened Blackbird Pizzeria, Philadelphia’s vegan scene looked radically different. You could count the city’s vegetarian mainstays on two hands. Strictly vegan spots were almost nonexistent. Yet Mebus, who had New York experience and Philly-area roots, believed in the city’s ability to embrace plant-based eating. And he was right. Almost a decade later, Blackbird has become a household name.