The M1911/1911A1 was the standard sidearm of the United States military from 1911 until 1985. The .45 ACP round, held in a 7-shot magazine, was first developed in response to reports during the Phillipine-American War of insufficient damage caused by the then standard .38 Long Colt cartridge. The 1911 was issued in WW1, while the slightly modified 1911A1 was adopted in 1924. Major differences between the two models include an altered grip (straight backed on the 1911, curved on the 1911A1), a slightly shorter trigger and hammer.
While the model featured in Wasteland was fictional at the time the game was developed, Colt did eventually release a Model 1991 pistol that was very similar to the original 1911 albeit with an updated safety mechanism.
In its current role, it has no trouble slowing down desert raiders or the occasional mutant cactus. Many Desert Rangers find this a perfect weapon to take with them when they first head into the wastelands.
It is also quite popular among various wasteland vagabonds, however its low magazine capacity makes the VP91Z 9mm pistol a better choice as a sidearm.