A Philadelphia mural entitled You Go Girl by Jetsonorama and Ursula Rucker. This is just one of many murals that the city's Mural Arts Program helped to create. Steve Weinik/Courtesy of the City of Philadelphia Mural Arts Program hide caption

itoggle caption Steve Weinik/Courtesy of the City of Philadelphia Mural Arts Program

Officials attend the launch of a Positive Train Control system for Los Angeles' Metrolink commuter trains in February 2014 at Los Angeles Union Station. Congress mandated the technology after a Metrolink engineer ran a red light while he was texting and crashed head-on with a freight train in 2008. Damian Dovarganes/AP hide caption

itoggle caption Damian Dovarganes/AP

Inside a Brown's Super Store. Brown's operates seven profitable supermarkets in low-income neighborhoods in Philadelphia. Courtesy of Brown's Super Stores, Inc. hide caption

itoggle caption Courtesy of Brown's Super Stores, Inc.

Emergency personnel search through the wreckage of an Amtrak train that derailed Tuesday night in Philadelphia, killing at least five people who were on board. Joseph Kaczmarek/AP hide caption

itoggle caption Joseph Kaczmarek/AP

Measles is highly contagious, and it produces fever and rash in susceptible people who become infected. Hazel Appleton/Health Protection Agency Centre/Science Source hide caption

itoggle caption Hazel Appleton/Health Protection Agency Centre/Science Source

New apartment buildings are replacing empty lots in Mantua, one of Philadelphia's poorest neighborhoods. Will Figg for NPR hide caption

itoggle caption Will Figg for NPR

Philadelphia City Councilwoman Maria Quinones-Sanchez pushed for the city to change its practice of detaining immigrants on behalf of federal officials. Matt Rourke/AP hide caption

itoggle caption Matt Rourke/AP