Sixty-six years ago today (on 1947-09-09) operators of the Mark II Aiken Relay Computer being tested at Harvard found a dead moth trapped between points of Relay #70 in Panel F. Dr. Grace Hopper made an entry in the Mark II log book and identified it as the "first actual case of bug being found". (source)

 

 

 

first computer bug

 

 

The log book is now at the National Museum of American History.