The Australian Rail Track Corporation says the repairs involved 100 staff working separate shifts around the clock for 24 days to restore 18 separate breaks after heavy rain and flooding across the state last month.
In some places, more than 200 millimetres of rain fell in a 24-hour period, with meteorologists describing it as a one-in-200 year weather event.
ARTC spokesman Simon Ormsby said all of Australia owned a debt of thanks to the crews and contractors who had worked extremely hard to bring the interstate network back online.
"Crews from Port Augusta led the charge with support by teams from Kalgoorlie, Adelaide and Port Augusta," he said.
"Contractors and staff from other areas were also called in to assist due to the overall scale of the operation."
Work crews shifted more than 50,000 tonnes of ballast and rock to complete the repairs and in some places were forced to re-build access roads to get heavy machinery to the site.
Nine freight trains were expected to access the repaired network on Tuesday allowing much-needed supplies such as fresh food and retail goods to move through the rail corridor.
The SA floods also closed the Stuart Highway, the main road access between Adelaide and Darwin, with several sections left submerged for days.
The highway began to reopen to heavy vehicles, 4WDs and light vehicles from late last week.
