The Highwomen are the rarest of country supergroups: a quartet who came together at the height of their popularity and creative powers, not when they were settling into their legacy. In that regard, the quartet of Brandi Carlile, Maren Morris, Amanda Shires, and Natalie Hemby differ from their knowing namesake the Highwaymen, a band Willie Nelson, Johnny Cash, Waylon Jennings, and Kris Kristofferson formed in 1985, just as they started to drift down the charts. When the Highwomen appeared in 2019, every member of the quartet was at a peak in her respective roots niche. Singer/...