The first road over the Blue Mountains that became part of today’s Great Western Highway was built in about six months. It was constructed by William Cox’s team and completed in January 1815 after work began in July 1814.

Quick Scoop

If you mean the original crossing from Sydney toward Bathurst, the answer is roughly half a year. Later upgrades, reroutings, and widening projects happened over many different periods, so the highway as it exists today was not built all at once.

A bit of context

  • The original road over the mountains was famously completed quickly in 1815.
  • The route was then rebuilt and improved many times in the 19th and 20th centuries.
  • Modern Blue Mountains upgrade work has continued into the 2020s and 2026, with parts of the corridor still being worked on or reopened in stages.

In one line

So, for the historic “build the road over the Blue Mountains” question: about 6 months.