PENRITH and St Marys will host the 200th anniversary celebrations of the Blue Mountains crossing this year.
The re-enactment, complete with period costumes and wagons, takes place with descendants of the original explorers from St Marys to Hartley across three weekends in May.
In 1813, Gregory Blaxland, William Lawson and William Charles Wentworth led the first European expedition to cross the Blue Mountains.
This secured a lifeline for Sydney to the western plains and saved the fledging British colony of NSW.
The Nepean Historical Society has been involved in the re-enactment planning from its beginning.
"Without that crossing the colony wouldn't have opened up, wouldn't have gone anywhere," the society's secretary, Beth Moore (pictured), said.
The society will place its own commemorative stone in St Marys on March 11.
"On March 9 there is the annual history conference in Penrith and this year's theme is the Blue Mountains crossing."
The conference will be at the Joan Sutherland Centre.
Speakers include Tracy Bedford of the Mitchell Library, David Blaxland, a descendant of Gregory Blaxland, and Wentworth biography author Andrew Tink.
They will discuss the lives of the explorers and what their crossing did for the colony.
"On March 25 and 26 we have a 'back to Emu Plains' weekend," Mrs Moore said.
"We are doing a historic walk through Emu Plains, and the history society will be producing a booklet on who's buried in the local cemetery.
"Nepean High School will be performing plays from the convict era."
Penrith Chamber of Commerce chief executive Jill Woods said the bicentenary provided rich opportunity for businesses.
"We were the gateway for explorers from Sydney to venture into different places and we still are," Mrs Woods said.
"The opportunities in this region are fantastic; Penrith is very well placed.
"There are a number of international and special events for people here."
In May the re-enactment starts with a traditional Aussie breakfast at Blaxland's Farm in St Marys. The actor Jack Thompson will join the celebrations.
There will also be a historic festival at Mamre Homestead in Orchard Hills and a camp-out on the Nepean River.