This plant used to be (and sometimes still is, depending on the source) in the Yucca genus, where it was known as Yucca whipplei or the Whipple yucca. It has recently been put into a separate and new genus. This particular species is found only in NW Arizona, on slopes of the Canyon. This plant is semelparous, meaning it flowers once, then dies, like an agave.
The plant in these photos is on the slope of a small drainage, about 2,000’ elevation. Definitive and up to date information for “Hesperoyucca newberry” is difficult to come by. One source I found is: