They were her first ever concerts FOR A FOLK AUDIENCE, and yes, among the few solo concerts she had performed at that point. Really very important events for the folk revival. Before that, she had been backing up her daughters, Gladys, June and the amazing Anita, working in commercial country music, doing Grand Ole Opry roadshows and such.
You can read about the concerts, and their significance, in Mark Zwonitzer, WILL YOU MISS ME WHEN I'M GONE: THE CARTER FAMILY AND THEIR LEGACY IN AMERICAN MUSIC (2002), pp.340-42.