ID this ornamental grass for me

I see a lot of landscaping around town with this big puffy ornamental grass type thing and I can't figure out what it is from the googles.

It seems to grow as a unit (maybe that makes it not grass?), so one plant equals one structure. It grows pretty large. Sometimes 3-4' wide, 4-5' tall. It has two "substructures":

1. a floppier grass growing from the center that gives it its width
2. an erect grass growing from the center that has a big frond of wheat looking puff on the top, giving it its height.

What is this?? It's my favorite and I want some.