In 2011, there were 196 murders in Baltimore, the lowest number since 1977. From the Baltimore Sun:
The drop extends an overall downward trend in gun violence here since 2007, the year Police Commissioner Frederick H. Bealefeld III took office.
…
During the crack-fueled drug wars of the 1990s, killings in the [Eastern] district sometimes topped 80 a year. Last year, there were 27 killings, and only one since Oct. 17 — nothing to brag about and yet a remarkable number for this beleaguered area.
…
The new priorities led to a sharp drop in arrests, with less than half as many people arrested last year than the 100,000 locked up in 2005.
St. Louis had a decrease too. Here is an interesting article about what StL has done with UMSL's criminology department.
stltoday.com/news/opinion/columns/the-platform/editorial-innovative-open-approaches-are-reducing-violent-crime/article_203926cf-ada7-5249-aada-1735d7a611d2.html
The all cash, 30k bail requirement for gun possession might be a useful tool in Baltimore as well.