According to Merriam-Webster's definition, a pumpkin could be any of these squash; Cucurbita pepo, Cucurbita moschata, or Cucurbita maxima. Both other brands of canned pumpkin on the shelf, Libby's and One-Pie, use Dickinson pumpkins (C. moschata), 30-100 lb. tan pumpkins known to be good for canning.
On the surface, the Dickinson pumpkin, Libby's variety, is unappealing. A misshapen, pale sibling to its brighter-colored brethren, the oblong Dickinson averages 20 pounds. It has ridges streaking the rind and looks more like a butternut squash. When ripe, the fruit's skin tends to be a dull gold or tan.
But inside, the sweet-smelling flesh is burnt orange. In comparison to other varieties of pumpkins, there is more flavorful meat per pound: The rind is thinner, the seeds are fewer and the hollow core inside each fruit is smaller.