Solid line = floor (spellings that unambiguously belong to the group). Shaded band up to the dashed edge = ceiling (the most it could reach if every ambiguous spelling counted here).
Dawn was more common in the past and has since settled at a lower, steady level. All-time it's been given to 468,737 U.S. babies, the 1,803rd most common name by sound today, peaking at 17,225 in 1970, with 174 in 2025.
By sound, Dawn also includes the spellings Don, Donn, Dawne.