For much of the last century, the making of a Thanksgiving pumpkin pie has begun with opening a can of Libby's; that 144-year-old Chicago-based company cans close to 50,000 tons of pumpkin every year. Say what you will about canned pumpkin, it has proven to be very good for the survival of pumpkin pie as the iconic Thanksgiving dessert. During the past decade or so, however, the proliferation of farmers' markets has made all sorts of cooking pumpkin available across the United States. The ones used by New England settlers and those grown today are all Cucurbitas, a genus of the gourd. Many of the pumpkins used for baking come under the species Cucurbita moschata, which includes low-moisture, creamy-fleshed varieties such as the neck pumpkin and the dickinson field pumpkin (the one that's typically canned), and even the butternut squash. Bake a pie using a jack-o'-lantern variety like magic lantern or appalachian, though, and the result will be a filling that's fibrous and vegetal.