Agave americana, probably the best known of the agaves, is the "Century Plant". It's called that because of the misconception that they take a century to bloom. In fact A. americana can bloom in as little as 15 years or take as long as 50. It's been so widely cultivated since the days of the early Spanish explorers, that it's origin is uncertain. Somewhere in eastern Mexico it's assumed. This is one of the largest Agaves, a single rosette can span 10 feet. Flower stalks have been reported as tall as 40 feet.
     I had a standard A. americana but took it out because it got too huge. The variegated one above has stayed much smaller and grows slower so it's OK for now. It's only about 18 inches across. I love the variegation. The picture below is of a much larger variegated one at the Desert Botanical Gardens in Phoenix. I forget the cultivar name right now.