The woman in "Unknown Legend" is Neil Young's wife (at the time), Pegi Morton Young
. The two met in 1974, while Morton was working as a waitress at a diner near Young's ranch.
The song talks about a waitress, now mother of two, who had once lived a life of travel and restlessness. The chorus harks back to her years of riding a Harley Davidson through the desert, with its chrome and steel "Collidin' with the very air she breathes." The song sounds both triumphant and sad. It laments the woman's situation ("Now she's dressin' two kids, lookin' for a magic kiss") while celebrating the wild rambling imagery of her past, all while sweetly observing her graceful movements across the diner floor.