This is a Yucca plant starting into its short-lived blooming season. I once heard a park ranger in Mesa Verde National Park refer to the Yucca plant as the Wal-Mart of the Puebloan people. They used this amazing plant for food, medicine, and clothes. Every part of the plant, from the flowers to the leaves to the roots, had a strategic use in their culture.
The plant grows a central stalk (seen here) usually in the late Spring time from whence the flowers bloom. All the flowers on a plant are usually all in bloom at once. The stalk dies after the flowering season, but might continue to stand throughout the winter.