The zig zag line operated between 1869 and 1910, to overcome an otherwise insurmountable climb and descent on the western side of the Blue Mountains.

The original plan by the Engineer-in-Charge of New South Wales Government Railways, John Whitton, had been to build a 2-mile (3.2 km) tunnel.

[1] After consideration of several alternate routes the Great Western Railway was extended along the high ridge of the Darling Causeway from Mount Victoria.

[1][2] On the eastern side of the range, the Lapstone Zig Zag, also designed under the supervision of John Whitton, opened near Glenbrook in 1867.

[3] By contrast, the Lithgow Zig Zag railway, built between 1866 and 1869, required much heavier engineering, including four large rock cuttings, three fine stone viaducts with 30-foot (9.1 m) semi-circular arches (originally four were planned, but one was built as an embankment instead) and a short tunnel (three tunnels were planned, but two were daylighted during construction due to leaks, becoming two of the four cuttings mentioned above).

[1] John Whitton and his work have been underrated in Australian history, although they provided the operational foundation of the main railway lines in New South Wales.

It was for the Clarence to Wallerawang section of railway which consisted of seven stone viaducts, varying in height from 3.0 to 21.3 metres (10 to 70 ft), three tunnels and nearly one and a quarter million cubic yards of excavations, two-thirds through rock.

George senior had been encouraged to migrate to New South Wales by Governor Macquarie who wished him to assist with government building works.

He worked on stone railway bridges at the Great Zig Zag and Marrangaroo, and married Marion Miles, daughter of one of the construction foremen.

After the failure of the deep lead gold boom of the 1870s George returned to the Lithgow valley and established a construction business with Thomas Crowe.

[5][1] On 19 October 1869 the first official train ran across the Lithgow Zig Zag to Bowenfels railway station, completing the route over the Blue Mountains.

At least one critic has opined that, while both the Zig Zag and the subsequent Ten Tunnels Deviation were magnificent works of civil engineering, these projects were aiming to solve the wrong problem.

Much of this route closely followed an earlier road survey made by Hamiliton Hume and, an assistant surveyor, Lieutenant George Bowen, in 1827.

[6] Even after the Zig Zag had been bypassed, banking engines were often needed to assist heavy freight trains over the mountains from Lithgow.

Eventually traffic became so dense, due to the growth of the railway system through the spread of settlement, together with the loss of time in working over the Great Zig Zag, that alternatives were considered.

The "top" wing was abandoned and a new line constructed which involved a sharp curve, heavy rock excavations and earth fillings to a depth of 60 feet (18 m).

The train was divided into two but the bottom portion accidentally became a runaway and eventually crashed into the rock cutting of Top Points.

[1] As at 30 September 1997, The Great Zig Zag Railway had a profound influence upon the development and economy of western New South Wales.

The reserve is a fine scenic attraction and the sandstone escarpments and viaducts provide a dramatic juxtaposition to the urban development of nearby Lithgow.

It is of historical significance because upon completion it triggered extensive development and had a profound influence on the economy of western New South Wales.

The reserve is a fine scenic attraction in itself, offering superb views of the rugged sandstone valleys and escarpments leading to the western plains.