Today we draw on the extensive archives of the Historical Society of Katherine Inc.to prepare to mark a moment in history.

It looks very lethargic today, but the Katherine River was for many decades a feared barrier to the interior of northern Australia.

All sorts of historic milestones are already being crossed as we count down to the centenary of the railway bridge which changed all that.

The "Lowie", the Low Level Bridge, was a war-time necessity in 1942 and the enormous concrete "Eugene Betti" bridge was a marvel when opened in 1976, but it's the railway bridge which continues to signpost Katherine.

Although it's a bit rusty looking, it is still standing strong and tall, just as it was when built almost 100 years ago.

Anyone who has stood on it during a high wet season flow can tell you it takes the torrent without a quiver.

It is simply an experience of a lifetime to stand in the centre of this century-old steel bridge in the middle of a maelstrom.

The tallest bridge on the railway line to Darwin, it was one of the major civil engineering feats of the time.

Actual building began in 1924 with a project cost of 94,000 pounds, worth about $7m today.

But preparation for construction began years earlier as a jobs scheme after the Great War.

According to documents held by the historical society, the Federal Government approved funds for the line across the Katherine River to link with Mataranka.

Rail began in the Top End to link Darwin to the Pine Creek gold rush but just as Burke and Wills wanted to walk from south to north, so was born a dream to span the continent by rail.

Even after the defences of the feared Katherine River were breached by a steel span, it still took another 80 years before the dream of linking Adelaide to Darwin was realised.

The approaches to this new Katherine bridge were completed by 1921, and work started almost immediately on other preliminary work.

Looking at the almost stalled Katherine River today, it is hard to imagine it was once believed an impassable obstacle to the interior.

Knotts Crossing (back of the Katherine Hospital) was fine for horses and stock as a natural river crossing in the dry season but the river rises quickly to become a torrent each wet season.

To cope with devastating floods, the designers built it 23 metres above the riverbed, with 7 x 31m spans. The disastrous 1998 flood peaked at 20.4m.

During the height of the 1998 flood, it was estimated enough water flowed under the bridge to fill Sydney harbor in 12 hours.

At the time of its construction it was built to handle standard gauge track.

It took two years to build between 1924-1926, and more than 500 men worked on the project.

Looking at the photographs still held by the Katherine Museum today of the heart-stopping methods used in construction, it is miraculous that no-one was killed in its construction.

The first unofficial train crossed on Christmas Eve 1925 and it officially opened on January 21, 1926.

It has never closed, not really.

It sleepers have been replaced by steel mesh but it is still a favourite platform for viewing the river, especially as it peaks.

Today it is also a billboard for the famous but fast fading "Jesus Loves Nacho" graffiti, and the river height measurements, checked by many people in either wet or dry season when crossing the concrete bridge.

Fergusson River celebrates 100 years of survival.

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