The milestone will be celebrated on Saturday with the Dance of the Decades ball, echoing the official opening of the bridge on April 6, 1935, which was observed with a ball in the Britannia Theatre.
Dance of the Decades ball spokeswoman Irene Mosley said on talking with several groups in town, everyone agreed the bridge deserved a special birthday event, and a dance was a suitable way to mark the occasion.
"Imagine what life would be like in Balclutha without the bridge," she said.
"It is our main icon and our life blood, and the fact that it has stood there for 75 years keeping our town humming is very important."
The dance will be a 1935-style dance, in the Balclutha Memorial Hall from 8pm till midnight, with attendees wearing formal attire from the 1930s, or any decade since.
Mrs Mosley said if you mentioned to someone "I come from Balclutha", they usually said "Oh, yes, it has a big bridge and I have driven over it.
"The bridge really does tower over the town," she said.
"We hope people will take the time to come along and have a fun night."
