The agave looks like the yucca. You can tell the difference by the tall 15 foot stalk of the agave compared to the short 2-4 foot stalks of Grand Canyon yuccas. Also, Grand Canyon agave leaves are angrily toothed along the sides. Many native American tribes eat the young stalk of the agave as well as roasting the "hearts." The flowers are edible as well.
Here are the agave leaves. For many years (15 to 25) prior to blooming, the leaf rosette is all you see. The plant dies after sending up the stalk and producing seed. An agave uses its last ounce of stored energy to reproduce gloriously, martyring itself for the progeny.
Here is the top of the blooming agave stalk. Stalks grow at a furious rate--over a foot per day.