I've never visited St. Louis, so I can't comment as to its safety. The only city I've ever been nervous in, however, was Philadelphia. The sad part was, I was in an extremely affluent section of town. I was also allowed the wonderful experience that is Camden on a trip from Philly to Atlantic City. Thanks to EXTREMELY disorganized road work and little to no signage indicating detours, I got to "experience" a great deal of that local. That being said, I have a hard time believing St. Louis is more dangerous than Camden.
Swoop