Final answer:
On September 18, 1848, Phineas Gage, a railroad construction foreman, suffered a traumatic brain injury.
Step-by-step explanation:
On September 18, 1848, a significant event in the field of medicine took place. It was the day when Phineas Gage, a railroad construction foreman, suffered a traumatic brain injury after an iron rod was accidentally driven through his skull. This incident provided valuable insights into the role of the brain in personality and behavior, as Gage survived the injury but experienced significant changes in his personality.