Use stream of consciousness to answer the following. The 2007 model year brought a complete redesign of the Jeep Wrangler, and also a four-door model. The TJ chassis was replaced by an all new JK platform. This next-generation Wrangler was noticeably wider than the previous model, with a 3.4-inch (86 mm) wider track; and though the two-door model has a 2-inch (51 mm) longer wheelbase, it is actually 2.5 inches (64 mm) shorter in overall length than the TJ, allowing for a 44.3 approach angle and a 40.4 departure angle. With a larger factory available tire size of 32 inches, the breakover angle on the Rubicon is increased from 22.6 to 25.4 . The four-door Unlimited model has an over 20-inch (510 mm) longer wheelbase at 116 in (2,950 mm) to offer much improved rear seating room, but is nevertheless only 2.4-inch (61 mm) longer than the 2006 TJ Unlimited.

When did they start making 4 door jeep wrangler?
The relevant information to answer the above question is: The 2007 model year brought a complete redesign of the Jeep Wrangler, and also a four-door model. Final answer: 2007.