Drive through the city and see visions of the past, present and possible future in murals and graffiti tags. Hundreds of them are legal works — sponsored by city-affiliated organizations and nonprofits. Others, under the umbrella "street art," are unsanctioned, often unsigned pieces — many making a political statement. It may be as simple as "No shoot zone" scribbled on the wall of a gas station, or as iconic as the "Whoever died from a rough ride?" billboard at North Avenue and Charles Street, painted after the death of Freddie Gray.