Cool chart showing the changing US murder rate over time

[pbrower2a]

what's up with the late 30s?

1. Rapidly-improving social conditions.

2. CCC projects that gave what would have otherwise been wayward kids work, pay, supervision, and meaning.

3. People were less desperate than they had been in the dreariest part (1932-1934) of the Great Depression.

4. Sudden improvement in police work. The FBI turned its focus on persons who violated the federal law proscribing interstate flight to avoid prosecution. Such made state borders less porous for offenders like Clyde Barrow and Bonnie Parker who may have lived in one state and committed their crimes in others.

5. Change in public attitudes toward criminals from semi-heroes to arch-villains. Criminals like John Dillinger and Bruno Hauptmann went from being seen as colorful rogues to arch-villains for killing bread-winners who had done nothing wrong -- and small children.

6. Repeal of Prohibition took away one of the cash cows for violent gangsters who enforced their will and territory through murder.

7. A heavy use of capital punishment for murder. Electric chairs and gas chambers were unusually busy. 

[pbrower2a]

Still way to go to reach 1900 levels again (and therefore European levels).

The 1900 stats are very dubious. Crime reporting wasn't all that consistent in theold days. If a black person was murdered, or lynched, local enforcement didn't always take it seriously. Also, denying that there is a racial element to the high American murder rate is rather counter-productive to anybody who sincerely cares about murders as a real problem. Oddly enough, it's also something only white people do. Black people, the overwhelming majority of whom are not murderers, of course, do not kid themselves about the problems in their communities. They know better than anybody what's going on.
Also, part of the drop in recent years is about improvements in medical treatment. It's only a murder if the victim dies. Trauma units can do amazing things today, and you see a similar reduction in deaths from motor vehicle accidents.

Don't forget Kevlar, the polymer behind -- or creating, more specifically - the bullet-proof vests that many police officers now wear. Crooks used to be able to shoot a cop in the lungs, heart, or abdomen  and leave a cop to die. Now the crook shoots at the cop's chest, and the cop shoots back at the would-be cop-killer who then dies -- or tries to shoot at the cop's head, which is still a fatal shot, but such requires that the crook take a more time-consuming aim than the cop, who then plugs the crook; this turns would-be cop-killing into suicide by cop.

As for deaths from motor vehicle collisions -- drunk or drugged driving is now prosecuted more automatically and at a lower threshold. Due to the building of expressways, vehicle collisions are less common and less severe. The head-on collisions that killed so many people on two-lane blacktops are becoming less frequent. Even the older state highways are being re-engineered with turn lanes that reduce rear-end collisions that can also kill. Collapsible steering wheels greatly reduce deaths from impalement of drivers. Seat belts are common and seat-belt laws are rigidly enforced. Child safety seats are the norm.  

As for law enforcement in the late 1900s -- it was far easier to get away with murder. Arsenic "inheritance powder" poisoning was much like cholera in effect... but today, arsenic residues in a corpse or even ashes give cause for investigation.