Northern section (Waterfall to Bulli Tops)

Construction of the section between Waterfall and Bulli Tops commenced in July 1970.^[4][5] At 22.9km, it was then the longest section of freeway to completed at one time, at a cost of $30.5 million;^[4] it opened as Southern Freeway on 24 July 1975, and was allocated Freeway Route F6 (which later allowed it to be locally known as the "F6 Freeway"). Financed by State Government bonds, this section of freeway initially incurred a toll from its opening.^[5][6] This part of the freeway did not feature the Helensburgh Interchange (which subsequently opened in February 2000). The toll operated for 20 years: this was 10 years short of its intended operating length, due to local residents complaining that the F3 Freeway had its toll dropped in 1988 (which was at the time intended to be dropped as its loans had been fully paid off, unlike those of the F6). After much pressure, the tolls were eventually removed on 30 July 1995, when the loans had been repaid.^[7] Remnants of the tollbooths could initially be seen at the old toll plaza at Waterfall, such as faint markings and a set of warning lights in the southbound direction for the toll plaza. These remnants have since been removed. However, as of 2021, the widened carriageways for the toll booths can still be seen at 34°09′02″S 150°59′25″E / 34.150476°S 150.990208°E / -34.150476; 150.990208.

To complement the tollway, the dual carriageways of Princes Highway from Waterfall north to Loftus and the Sutherland bypass were constructed and opened to traffic on 16 September 1975.^[4]

Central section (Mount Ousley Road)

The section between Bulli Tops and Gwynneville was previously named as part of Mount Ousley Road,^[8] and is still often referred to as such.^[9] Mount Ousley Road was built in 1942 as a defence route, involving the reconstruction of part of a 19th century route from Bulli Tops to the Picton-Mt Keira road (the southern section not incorporated into the defence route is Clive Bissell Drive), and the construction of a new section of road to descend the escarpment and terminate at Princes Highway at North Wollongong (the easternmost 3.5 km of Picton Road, from Mount Keira Road to Mount Ousley Road, was also constructed as part of this project).

From the 1960s to the 1980s Mount Ousley Road was gradually upgraded,^[8] initially by the construction of overtaking lanes, then the staged extension of the overtaking lanes to ultimately provide continuous two lanes in each direction, and a third lane northbound from the foot of Mount Ousley to Clive Bissell Drive and a third southbound lane from Clive Bissell Drive to New Mount Pleasant Road. This was followed by deviations to replace sharp curves on steep gradients on the northern approach to Bellambi Creek and both approaches to Cataract Creek. A continuous Jersey median was subsequently installed in stages. Extensive truck management measures were also installed on the long, steep descent from Clive Bissell Drive into Wollongong during the 1980s, following a number of fatal truck crashes on this section.

The Mount Ousley Road section of Princes Motorway is sometimes not considered part of the freeway proper,^[4] as it is not built to full freeway standards, containing left-in/left-out intersections and the at-grade intersection at the foot of Mount Ousley, where the motorway proper diverges from Mount Ousley Road.^[8] This intersection is proposed to be replaced by a grade-separated interchange: the federal government announced funding for the interchange in May 2021, relocation of utility services is underway, and major construction is expected to start in 2024.^[10]

In November 2015, it was announced that the section between Bulli Tops and Picton Road would have a third lane added in each direction.^[11] As of 2019, detailed design works have been completed.^[12]

Southern section (Gwynneville to Yallah)

The construction of the first stage of Princes Motorway between Gwynneville and Yallah commenced in May 1959. This formed the majority of what was built as a north-south bypass of Wollongong central business district,^[4] and was the first section built of the Northern Distributor, an arterial road planned to run from Thirroul in the north to Dapto in the south. The CBD bypass was opened from Princes Highway at North Wollongong to Foley Street in December 1959,^[4] from Foley Street to Phillips Avenue in 1961 and from Phillips Avenue to Princes Highway at West Wollongong in July 1963.^[4] Duplication of the Northern Distributor from Gwynneville to West Wollongong was completed in 1965.^[4] The Northern Distributor was allocated as Freeway Route F8 in 1974, extended further north from the 1980s, and renamed Memorial Drive in 2010.

In March 1964 a connector road from Mount Ousley Road at the foot of Mount Ousley to the Northern Distributor in Gwynneville was opened as single carriageway road, and was duplicated in the early 1970s. The intersection with the Northern Distributor was later reconstructed to a grade-separated interchange, beginning in April 1996 and opening in December 1998.

Following completion of the Mount Ousley-Gwynneville connector, Southern Freeway subsumed a section of the Northern Distributor south of Gwynneville to West Wollongong, and continued making its way southward, then with the extension from West Wollongong to The Avenue at Figtree opening in 1967, and then from Five Islands Road to Northcliffe Drive in 1973 (albeit as a single carriageway, with duplication finished in 1975). The intermediate section from The Avenue to Five Islands Road, including the interchange with Masters Road, was opened in 1975; this section was also allocated Freeway Route F6 (which also allowed it to be locally known as the "F6 Freeway") in 1974. Construction then continued south from Northcliffe Drive to Kanahooka Road in 1978 (with duplication concluding in 1979), to Fowlers Road in 1981 (with duplication concluding in 1983), to Princes Highway near Tallawarra power station in 1986 (with duplication concluding in 1987),^[4] and to Yallah (in conjunction with grade separation of the junction with Princes Highway) in 1989.

As Princes Motorway

The passing of the Main Roads Act of 1924^[13] through the Parliament of New South Wales provided for the declaration of Main Roads, roads partially funded by the State government through the Main Roads Board (later the Department of Main Roads, and eventually Transport for NSW). With the subsequent passing of the Main Roads (Amendment) Act of 1929^[14] to provide for additional declarations of State Highways and Trunk Roads, the Department of Main Roads (having succeeded the MRB in 1932) declared Southern Freeway as a motorway (under plan number 6006), on 8 October 1975,^[2] and was re-declared to cover each extension until it reached its southern terminus in Yallah; the motorway today still retains this declaration (under Motorway 6006).^[15]

Freeway Route F6 was allocated to the southern section of Southern Freeway in 1973, and along the entire northern section when it opened in 1975: as new sections of the freeway opened, Freeway Route F6 was extended along these new sections, but had already begun to be phased out in the mid-1908s to be replaced by National Route 1, and had disappeared by 1992; the Mount Ousley Road section was designated part of National Route 1 from 1975. With the conversion to the newer alphanumeric system in 2013, National Route 1 was replaced with route M1, and Southern Freeway and Mount Ousley Road were officially renamed as M1 Princes Motorway.^[16]

Albion Park Rail Bypass

At the southern end, Princes Motorway was extended to Oak Flats via a 9.8 km bypass of Albion Park Rail.^[17] The bypass completed the 'missing link' in the four-lane road between Sydney and Berry (currently being extended to Bomaderry),^[17] and was constructed on a corridor which was identified by the Roads and Traffic Authority in a study in the mid 1990s. In 2013, Roads and Maritime Services (successor to the RTA) confirmed the reserved corridor to be suitable for the bypass.^[17]

The bypass was completed on 9 October 2021, several months ahead of schedule.^[18][19] The section of the bypass between Yallah and the Illawarra Highway (Terry Street) interchange was opened to traffic in May 2021.^[20][21][22] The northbound carriageway of the remainder of the bypass (ie north from the New Lake Entrance Road interchange to the Illawarra Highway interchange) opened to traffic on 7 August 2021.^[23][24][25] The remainder of the southbound carriageway was opened to traffic on 9 October 2021, thereby completing the bypass.^[17][26]

Northern extension

Captain Cook Bridge

Taren Point Road

The six-lane Captain Cook Bridge (connecting Sans Souci to Taren Point) and a short joining section of Taren Point Road to the south are the only parts of the extension to be built

The County of Cumberland planning scheme of 1948 outlined an F6 extension from the current-day end-point at Waterfall.^[27] As such, an F6 corridor was set aside that passes through the Royal National Park from Waterfall to Campbell Road in St Peters. The land reservation tract currently passes through the suburbs of Loftus, Kirrawee, Gymea, Miranda, Taren Point, Sandringham, Sans Souci, Ramsgate, Monterey, Kogarah, Brighton-Le-Sands, Rockdale, Banksia, Arncliffe, Kyeemagh and Tempe.^[28]

Of the proposed extension, only the six-lane Captain Cook Bridge and a short connecting section of Taren Point Road to the south have been built. Establishment of the bridge section of the F6 extension began in 1962, expedited to replace the ferry service that had operated from Taren Point to Sans Souci since 1916. Captain Cook Bridge was opened in May 1965.^[29]

In the original plan, the F6 would have connected to the Western Distributor.^[30] Then, in August 1977, premier Neville Wran cancelled the inner section of the F6 link, which at the time had an estimated construction cost of $96 million.^[29] At the same time, Wran announced that the inner section reservation would be sold off and the proposed extension would instead terminate at St Peters, a medium density industrial suburb.^[29][31][32]

Prior to the 2007 federal election, the Liberal–Nationals (Coalition) government promised to allocate $20 million towards planning for the F6 extension.^[33] Although the Coalition lost the 2007 election,^[34] the funding was once again promised at the subsequent 2010 federal election. This funding would ensure the project is "shovel ready" when funding becomes available.^[35]

In the mid 2010s, the F6 extension project was revived under the Liberal–National coalition state government. This project has since been renamed M6 Motorway.