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).
Harrison
Harrison has stayed fairly steady in American naming for generations. All-time it's been given to 99,462 U.S. babies, the 242nd most common name by sound today, peaking at 3,670 in 2016, with 3,080 in 2025.
Harrison has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).