It is a prosaic roadway that connects Perth city from north to south, but the development of the causeway bridge was crucial to the development of the colony.

In 1829, the area in the Swan River now called Heirisson Island was initially two islands surrounded by mud flats, and called Matagarup by the traditional Noongar owners.

The first bridge over the causeway in Perth, circa 1862. ( Supplied: State Library of WA )

"The river was totally unnavigable at this point for the early colonial settlers," explained Richard Offen from Heritage Perth.

"If they wanted to get up to Guildford, further east, they had to drag their boats over the mud flats.

"I'm sure from the very early days of the colony people were saying 'when are we going to get a bridge?'

"It took a little bit of time but at a meeting of the Roads Board Trust in February 1839 a motion was passed for "the erection of a bridge and causeway across the flats at Perth, which is a very real utility, and would materially benefit the Settlers throughout the Colony'."

By 1843 the first causeway and two bridges on the northern and southern sides had been built, the flats had been consolidated on Heirisson Island and the river dredged somewhat for river boats.

A toll was charged to almost every person who used the bridges, including pedestrians.

Farmers were charged for each head of livestock that crossed and the only exceptions were for soldiers in uniform and mail carriers.

The north side of the second causeway bridge, taken in approximately 1868.. ( Supplied: State Library of WA )

It became known as simply "the Causeway" and changed transport in the early colony.

"It created a better connection between Guildford, the Upper Swan, York and Fremantle," Mr Offen said.

"It was even suggested that plots of land on the islands could perhaps now be rented for summer gardens and small homesteads.

"However, by the 1860s the bridge was in 'a moribund state' according to the local papers and in 1862 it was almost completely submerged in some very serious floods.

"This clearly weakened the bridge. It was also very narrow and there were often accidents involving horses and carts.

"In 1867 a Mr E.C Loftie was fined forty shillings for causing an obstruction on the causeway.

"It turned out the herd of cattle he was driving got frightened and wedged themselves between the railings so that they could not be moved for over an hour."

View of the Causeway, Perth looking across the bridge to Victoria Park, 1906. ( Supplied: State Library of WA )

A new causeway, designed by colonial Superintendent of Public Works Richard Roach Jewell, was built by convict labour and opened in November 1867.

"The bridges were constructed of Jarrah, but, because of lack of funds, much material from the original bridge was reused, which meant that it was a bit weak," Mr Offen said.

"They actually drew the jarrah piles from the river out for the new bridge, and they were still in extremely good condition.

"Although the new structure was much better than the original, it was still quite narrow and uneven and there were weaknesses in it, and it was repaired umpteen times."

The causeway was widened in 1905 so that trams could cross to Victoria Park on the south side and it was widened another 10 feet in 1932.

Construction of the causeway from Victoria Park to Perth, 1951. ( Supplied: State Library of WA )

"By the mid-1930s however, the bridge was in very poor condition for traffic, which included motor vehicles by then, and there were great concerns," Mr Offen said.

"As a result of work to create new, deeper river channels, taking place as part of the Swan River Improvement Act, a site was chosen upstream of the original bridges for a new bridge.

"It was decided in the 1930s but World War II put a halt to everything."

Work eventually began in 1949 and the steel and concrete bridge, still used today, opened in 1952.

Two roundabouts were added at each end to ease the flow of traffic into the roads.

In 1998 the bridges were placed on the Western Australian Heritage Register.

Major patching of cracks in the concrete piers was done in 2004 to extend the life of the bridges, which carry thousands of vehicles every day.

On 'What's all that about?' Lorraine Horsley explores a hidden part of Perth's past, every Monday at 7:15am on 720 ABC Perth Breakfast.