The first photo is of the El Paso police from 1917 in front of their paddy wagon and the second is a modern SWAT Team.

As the first photo shows, it was once standard practice for police officers to wear long jackets to cover up their guns, apparently lest they offend civilians. The cop of the beat in just about any Hollywood movie in the 1930s dressed similarly. Apparently, this was a vestige of an anti-militarist tradition. Now, of course, the police seem to proudly brandish their guns in public at every opportunity.

Does anyone know any of research on when and why the shift from the old tradition of covering up guns? Who pushed the change and who, if anyone, opposed it?