The GMC Sierra was a series of full size pickup trucks introduced for the 1988 model year. Previously, GMC had used the Sierra name to designate their top trim level, but in 1988, the Sierra became its own model. The Sierra has been built in five generations, the first of which was based on the Chevrolet C/K, and the most recent four being based on the Chevrolet Silverado. Over the course of production, the Sierra has been offered in light-duty, medium-duty, and heavy-duty (known as 1500, 2500, and 3500 respectively), and with a range of different cab configurations. The five generations of Sierra are as follows: 1st Gen (1988-2002), 2nd Gen (1999-2007), 3rd Gen (2007-2013), 4th Gen (2014-2019), and 5th Gen (2019-).