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).
Florence has been climbing in recent years. All-time it's been given to 340,547 U.S. babies, the 901st most common name by sound today, peaking at 11,350 in 1918, with 796 in 2025.
Florence has no common alternate spellings by sound.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).