How much prairie land is there actually?

I quite interested in the American prairies and i've been looking at the satellite imagery and streetview of certain states and it seems to me like a lot of the land is fields and such - judging by the continuous squares, but then again when i streetview there, it sometimes looks like a prairie, and when i streetview somewhere where it seems like a prairie on satelitte it's the opposite.

So how much prairie land is there really?