 The contract to build the Great Zig Zag was awarded to Mr Patrick Higgins in May 1866.It was for the Clarence to Wallerawang section of railway which consisted of seven stone viaducts, varying in height from , three tunnels and nearly one and a quarter million cubic yards of excavations, two-thirds through rock.George McGarvie Donald of Lithgow was a master stonemason and builder who helped create the city of Lithgow.