Hi steve, just noticed your post and see it hasnt been answered, so a little late but its an Agave americana, commonly called 'The Century Plant' because its said it takes 100 yrs to flower but infact it will flower in about 12-15 yrs. the rosette that flowers then dies but as they produce lots of basal rosettes, there will always be plenty of others to replace it.
They are quite hardy when they get bigger than 2-3ft across, especially down here in the Southwest, thier main requirement is a sunny, very free drained spot, so lots of grit incorporated when planting, they rarely die from lack of water even in the driest of conditions ( all thier water is stored in the leaves) in Mexico where they come from, its the fermented leaves of this plant that the locals use to make tequila
hope this is not too late, lannerman