The vehicle we call the Jeep Wrangler has evolved quite a bit over the years. The monsters we drive today can trace their line all the way back to the first prototypes produced in 1940 (Production models started rolling off the production line in the fall of 1941). The US Army put out a request for bids to make a Command/Reconnaissance vehicle and thus an American Icon was born.
After WWII, the Willys Overland Company started selling civilian versions of their now iconic Willys MB, calling it the CJ-2A. From 1946 to 1985, the various Jeep versions carried the CJ designation symbolizing a "Civilian Jeep".
With the introduction of the Jeep Wrangler, the letter designations ceased to have any meaning to anyone other than the manufacturer. This hasn't kept people from putting their own words to the letters: YJ = "Wide Jeep", TJ = "Tough Jeep", JK = "Jeep King", and some other not so friendly terms that won't be mentioned here.
Note: In addition to the Wrangler models listed, the list of the various editions is by no means all-inclusive and are not listed in any particular order. I've tried to list as many as I can but some were only available for a very short time and may get left out by mistake. There have been more Jeep models than the version currently called "Wrangler" (the Wrangler name was first used with the models beginning in 1987). The following information has been edited from Wikipedia
, so if you want more info. on the other Jeep models, you can follow that link.