I did the same thing - also missed Porter Wagoner when I typed Waggoner, and I typed Shephard and Shepherd. I thought I typed Trisha Yearwood, but must have spelled it wrong, too. I could have used more time on this one. So many great ones I missed. Next time I'll only type last names.
How was this list compiled? On what planet is Boxcar Willie bigger than Webb Pierce? How does Gillian Welch make the list at all? She has never had a country hit.