why does the 1911 have an external hammer?

[Croyance]

Shootcraps, the Glock and many other striker designs must be dry-fired to field strip, IIRC. No need on the 1911.

 

[AZ Jeff]

When the M1911 was designed, the US Army still had a cavalry, believe it or not. The idea behind an external hammer was, among other things, so the mounted trooper could cock the hammer by rocking the pistol against his saddle/boot/leg/whatever.