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).
Shelby is now well below its former popularity. All-time it's been given to 176,355 U.S. babies, the 1,022nd most common name by sound today, peaking at 11,660 in 1991, with 511 in 2025.
By sound, Shelby also includes the spellings Shelbie, Shelbi.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).