Well, it's not really my field so I'll readily stand corrected (usually you'll find me in the revolver forum) but I'll try to throw some more stuff out there for you. John Browning (yup THAT Browning) came up with the design originally for Colt in 1911 (or at least that's when it first came out). The Colt 1911 saw use as a military side arm for years (don't know what years or how long but someone can probably fill you in on that). Now many different firearms companies make a version of the 1911: Colt, S&W, Kimber, Springfield, Para Ordinance, and Taurus is/has developed one and there are several others. All of these share a common design and at least closely resemble one another. The original design and most all of the later "copies" are single action only, although Para Ordinance I know had a double action only version. One of their more appealing features to many over the years has been their ability to be carried "cocked and locked" with the hammer cocked and the safety on, allowing you to quickly flip the safety off and give a light, short trigger pull.