The Steam Whistle
Imagine being awakened each morning by the squeal of a very loud whistle. KU students in the early 1900s were subjected to just such a thing.
Originally, the steam whistle's intent was to get students up each morning at 7:45 (it also signaled when evening curfew began). But in 1912, that changed. Instead of serving as an alarm clock, it now would be used to signal the end of hourly classes. It's been that way ever since.