The delicious, but seasonal sandwich was created in 1981. McDonald's had just hired an executive chef off of a luxury hotel and tasked him to create new menu items. One of his most famous creations: the McRib, was a result of ANOTHER one of his genius creations: the McNugget.
When the McNugget was created in 1979, it was so well received that every franchise wanted to carry them. At the time, they didn't have enough chicken supply to spread them around, so they had to come up with another menu item to give to those who couldn't get their hands on McNuggets.
The McRib itself was inspired by southern BBQ cuisine, down to the rib-like shape that the meat patty. Today, the McRib is an expected part of the fall season, and I'm sure many of you enjoy its delicious goodness.