I went to a very small Catholic high school outside of Green Bay, WI, which no longer even exists. Our most well-known alumnus probably wasn’t that well-known: Ted Fritsch, Jr., who played in the NFL for 7 years as a center and long-snapper.
My college alma mater is the University of Wisconsin-Madison, which has a number of famous alumni, including:
11 Nobel Laureates, including Saul Bellow and John Bardeen (the only person to win the Physics Nobel twice)
Actor Don Ameche
Rock guitarist Steve Miller (left before he finished his degree)
Architect Frank Lloyd Wright (attended, but did not graduate)
Aviator Charles Lindburgh (maybe; he’s listed on the Wikipedia list, but I can’t find corroboration)
Astronaut James Lovell
Author Joyce Carol Oates
Hockey player Chris Chelios
Olympic track star Suzy Favor-Hamilton
Football player Elroy “Crazy Legs” Hirsch
Of those, the most famous are probably either Wright or Lindburgh.
High School – possibly me. It’s a small school and few go on to any sort of fame, so the bar is pretty low. It could be my aunt, who played Carnegie Hall.
HS - no one I know of.
Did my undergrad at Oxford, so God knows who’s the most famous alumnus. God himself maybe, I think he did an exchange year there. Or Jesus, they did name a college after him afterall.
PhD was at University College London, probably loads of famous graduates but the political philosopher Jeremy Bentham is very prominent in the history of the place - statues etc. I think he may have been involved in founding it from memory.
University of Washington has too many to name, but here’s my best guest:
Bill Gates, Sr.
Frank Herbert
Warren Moon
Fred Hutchinson
Kenny G (couldn’t someone else take him??)
Rainn Wilson
Kyle MacLachlan
Gregory “Pappy” Boyington
Probably the most famous is Dean Koontz, but we also had Steve Spence (marathon runner), Jeanne Shaheen (Governor/Senator from New Hampshire), Chris Raab (from Jackass), Tommy Franks and Jay Garner. Shippensburg is a popular school to get a Masters Degree in Public Administration from with the officer corps from the US Army War College in Carlisle.