How to read the band →
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).
Mildred
Mildred is now well below its former popularity. All-time it's been given to 452,998 U.S. babies, the 2,236th most common name by sound today, peaking at 18,099 in 1920, with 98 in 2025.
Mildred has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).