The bridge crosses some 700ft above the River Avon below
Some 150,000 Bristolians gathered on the banks on the River Avon 145 years ago to watch history in the making.
The Clifton Suspension Bridge, designed by Isambard Kingdom Brunel, opened on 8 December 1864.
The Lord Lieutenant of Somerset, the Earl of Corke, and the Lord Lieutenant of of Bristol, the Earl of Ducie led a procession "to signify the unification of the two counties".
While the great and good of Bristol went for a party at the Victoria Rooms, the real star of the day crossed the bridge for the first time.
Hanham's Mary Griffiths, who was 21, raced a young man across to become the first member of the public to cross the bridge.
The real tragedy, though, was that Brunel himself did not live to see his bridge open.
The famous engineer died some five years before it was completed.
Dave Anderson, the current bridge master, told BBC Bristol: "It's a very important bridge for everybody in Bristol, not just for me.
"It's so dramatic, such a lovely setting, and I think the bridge means different things to different people.
"To many people it's just a very beautiful, elegant structure - people love to look at it."
Brunel designed many viaducts and crossings along the Great Western railway line but the River Avon crossing will perhaps be remembered as his biggest achievement.
One of the real surprises of the bridge was the fact he designed it when he was just aged 24.
"For somebody so young to have gained so much experience, confidence and knowledge to be able to design it at that age is quite impressive," said Mr Anderson.
"The civil engineer of today has a raft of design codes to help them.
"They set out what loads should be considered and what factors of safety to use and the strength and properties of the materials are.
"Brunel didn't have very much of that; he had to work it out himself."
Can the famous bridge last another 145 years? Mr Anderson believes that Brunel's design could stay the course.
"The roadway is a little narrow but traffic can get across safely and we do carry about 10,000 vehicles every day without any problem.
"The bridge has got plenty of strength - we're lucky, probably, that the bridge is overdesigned. That's why it's lasted so well for 145 years."