When the Lewis and Clark Expedition was going hungry, or existing only on meat, they bypassed a readily available food.
Yucca grows throughout much of the western plains. The root is edible by simply boiling it in oil. Just cut it in pieces and drop it in the oil. After a minute or so the pieces pop to the top with a nice golden-brown color, kind of like potato chips They are ready to eat.
But they were bypassed because everyone thought they were only good for soap. Frontiersmen as well as the natives of the prairies boiled their foods in water. Yucca roots boiled in water are not edible, they just foam away. But if oil is used instead of the water, they are a good vegetable to eat.