Which biome occurs in the united states and once contained huge herds of grazing herbivores

I have 2 answers:

answer 1: Its grassland because the grasslands have lots of grass and plants right? So then herbivores would go there and start devouring grass and plants and stuff like that.

answer 2: It can also be the rain forest because the rain forest has lots of fruit such as bananas and mangoes. Monkeys eat hem and other animals do to like us ... except we don't live in the rain forest.