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).
Kingston has stayed fairly steady in American naming for generations. All-time it's been given to 46,599 U.S. babies, the 335th most common name by sound today, peaking at 3,422 in 2021, with 1,725 in 2025.
Kingston has no common alternate spellings by sound.
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).