Each was built to a standard design and layout, although the Argyle Street substation was externally rendered to match the Sydney Harbour Bridge.

[1] As the suburban railway lines were converted from steam to electric traction, substations, located approximately 8 kilometres apart were required for efficiency in direct current (DC).

The original bridge lighting was installed by New South Wales Government Railways and was supplied to designs by the Department of Public Works.

The buildings remain relatively intact externally and internally and continue to serve the Harbour Bridge and electric train tunnels.

In 1924 preparations for the construction of the bridge began and as a result Dawes Point and The Rocks area was subject to a continuous stream of building work and whole streets were levelled and altered.

The ground floor is accessed via steel roller shutter doors on the north and south sides of the building, wide enough to allow equipment to be moved in and out.

[1] The switchhouse, located south of the substation, is a single-storey rendered structure with steel-framed windows and a gabled hip tiled roof.

The switchhouse includes a single example of a Reyrolle Oil Bath Motorised Switch (no longer functioning) and a row of modern switchboards.

In the substation a timber phone box, a switchboard, a framed plan of the Sydney Harbour Bridge and a large overhead gantry crane remain.

[1] The Argyle Street Railway Substation was listed on the New South Wales State Heritage Register on 2 April 1999 having satisfied the following criteria.

The Substation's prominent location emphasises its role in the service of the bridge and the railway, and acts as a landmark in the Millers Point urban landscape.

Of the fifteen substations constructed between 1926 and 1932 it is the only one of its type in terms of design style and rendered finish to match the Sydney Harbour Bridge which it was built to service.