The Nissan Altima is a staple of the midsize sedan class, but that hasn't always been the case. From the model's humble beginnings as a compact sedan to its rebirth as a midsizer in the early 2000s to the new 2019 iteration that offers cutting-edge engine tech and all-wheel drive, this photo gallery covers all six generations of the Altima. Take a look back at the popular four-door's history below.