A spokesperson told Global News that emergency crews were called to Catharine Street South and Main Street East just before 3:10 p.m. on Saturday.
The spokesperson said a 58-year-old man was hit by the sign.
Paramedics took the man to a trauma centre in Hamilton with critical injuries.
A 54-year-old man was also hit by the falling sign and suffered minor injuries.
It’s not clear if weather conditions caused the sign to come down.
A wind warning was issued by Environment Canada at around the time of the incident.
© 2018 Global News, a division of Corus Entertainment Inc.