Peter Muise recounts the hardier pies of yore, so tough that all the pies New England wives made could be stored in the root cellar - without a tin - for weeks:
Rye grows better in our climate than wheat, so rye flour was the most commonly used flour here. Have you ever baked with rye flour? It is much, much harder than wheat flour, so imagine making a fat-free rye flour pie crust. It was probably like edible ceramic.