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).
Sofia
Sofia climbed for decades and has been a steadily popular name ever since. All-time it's been given to 186,931 U.S. babies, the 55th most common name by sound today, peaking at 9,711 in 2015, with 8,261 in 2025.
Sofia has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).