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).
Morgan
Morgan is now well below its former popularity. All-time it's been given to 269,269 U.S. babies, the 436th most common name by sound today, peaking at 12,135 in 1995, with 1,509 in 2025.
Morgan has no common alternate spellings by sound.
Rising
Source: U.S. Social Security Administration, “National data” baby-names files (1880–2025).