Most people would call that Agave americana variegata, but it is possible that it is actually a variegated form of Agave mapisaga. A. americana can get big, but not really that big... is the argument that people make to suggest it is mapisaga instead. However, I have seen some regular americanas at Boyce Thompson Arboretum that were pretty close to 9-10 feet tall, in part because the made a bit of a trunk...
So it could just be a variegated americana in ideal growing conditions... the pups surrounding it would certainly argue for that.
