Agave angustifolia 'Marginata' on the left. Mom has one of these in her yard that she got from a plant that Grandma grew back in the '70's.
Agave americana var. 'americana' 'marginata'
Agave americana is also called a century plant. They flower after a century (or so). When an agave flowers, it grows a tall stem from the center. After flowering the original plant dies.
Here's another one flowering.
Tequila is made from one species of agave in Mexico.