"I went with Grandma, and when we got close to where the ribbon was to be cut, she grabbed me by the ear, pushed me forward, and said: 'Watch! You'll never see this again', and I got to watch the ribbon being cut."
Mr Mills has crossed the bridge almost every day since and will be on hand today when the bridge's birthday is celebrated in conjunction with the fourth annual Big River Festival.
In 1935, Mr Mills lived on Lanark St, opposite the Balclutha School gate.
"My grandparents lived in Paretai and came to see the opening," he said. "I don't recall walking across the bridge, but . . . from what I recall, the ribbon was blue. I understand there were official parties at each end of the bridge who met in the middle."
As part of the Big River Festival, the South Otago Museum will exhibit images of the bridge under construction and its official opening.
South Otago Museum curator Gary Ross is using the occasion of the 75th anniversary to contact living descendants of the bridge builders and people who were there on the day it was opened.
Mr Ross is gathering material and recording oral histories from people who experienced the building and opening first-hand.
"I've met four of five of the living people that were there, and they've given me anecdotes."
One of those was Mr Mills, who said the bridge had been a big part of his life.
He had crossed it most days for school and work.
"I've been over the bridge the correct way and the wrong way, and I've been under the bridge the correct way and the wrong way. Because of what the bridge is, a number of kids went over the arches on the way to school."
Mr Mills denies being one of those children.
However, he does admit using the bridge as a launching pad.
He had great fun dropping vegetables down the hole of lowered smoke stacks as ships passed under the bridge.
SS Clutha 2, piloted by Captain Kazuyuki Tsukigawa, went up and down the river.
Its smoke stack was on hinges so it could be lowered when it went under the bridge. The top of the stack had a grille over it, but when it was lowered, there was an open hole.
"We dropped turnips, cabbages, apples and things like that, but never any rocks. They went shoop into the hole.
"Mr Tsukigawa was a very religious man, and I'm sure he used to get very close to swearing at us in Japanese. He would see us and start waving his finger at us as he was coming towards the bridge," Mr Mills said.
"We did this a few times, then one weekend my grandparents decided to take us on a picnic, up the river. We got on the boat and my grandmother said to Mr Tsukigawa, `This is my grandson'.
"Mr Tsukigawa said `I think we have already met'."
Balclutha Bridge
Opened: April 6, 1935 by Minister of Public Works John Bitchener
Designer: William Langston Newnham
Design: Six-arch ferro-concrete bowstring
Concrete: 4358cu m (5700cu yds)
Steel: 528 metric tons (520 tons)
Total length: 244.1m (801ft) from end to end of abutments
Arch spans: 37.7m (123ft 8in)
Road width: 6.7m (22ft)
Total weight: 10,831 metric tons (10,660 tons)
Total cost: 40,871 10s 10d
