Spectacular celebration marks Golden Gate Bridge 75th birthday

Tens of thousands of tourists have celebrated the 75th birthday of the Golden Gate Bridge in an all-day festival that climaxed with a spectacular display of fireworks above the world-famous orange structure.

Well-wishers crowded the surrounding shoreline and traversed the almost 3km length of the bridge's crowded footpath throughout Sunday as a flotilla of boats, including World War II battleships and small pleasure craft, cruised in the San Francisco bay waters underneath the bridge.

The bridge remained open to vehicle traffic throughout the festivities as authorities sought to avoid a repeat of the 50th anniversary celebration in 1987, when 300,000 people crammed onto the bridge at once, causing its gently arched central roadway to flatten under the weight.

"Everyone is biking and walking and looks very happy," Mary Currie, public affairs director for the Golden Gate Bridge, Highway and Transportation District, told reporters.

The only damper on the festivities was the usual blanket of wind and fog that often shrouds the structure, and which obscured the sun until the afternoon.

The art deco bridge was opened in 1937 after four years of construction at a cost of $US35 million.

At the time it was the longest suspension bridge in the world, holding that record until the opening of the Verrazanno-Narrows Bridge in New York City in 1964. It now ranks as the world's ninth longest suspension bridge.