The early convicts transported to Sydney found themselves in a vast natural prison. Anyone thinking of escape faced the Pacific Ocean to the east and the Hawkesbury and Port Hacking river systems to the north and south. But it was the Blue Mountains to the west that presented the greatest challenge.
For many years the sheer cliffs, deep gorges, thick scrub and river rapids of the Blue Mountains defeated Europeans keen to find new lands and cattle pasture as well as convicts trying to escape to the west.
With none of the European colonists able to cross the mountains rumours began to circulate about what was on the other side. One of the more popular was talk of a vast inland sea on the other side of the range. Other more practical minds felt finding a crossing could open up new grazing land allowing farmers to expand the settlement.
The first explorers
Among the first to explore the Great Dividing Range was the paroled convict Matthew Everingham. He had arrived with Governor Phillip on the First Fleet and after becoming a free man was given one of the first land grants at “The Ponds” near present day Dundas. Why he decided to explore the Blue Mountains is not clear. He had been convicted of forgery while working as an attorney's aid and had no previous exploring experience but he writes in his letterbook that in October 1795, he and two friends, Ramsay and Reed set off;
With a determination to see ye cattle and to cross the blue mountains of this country ... hauling lines to each other to support and catch them in case of slipping, which they were very apt to do, but were obliged to give it up as impossible, after clambering over twelve or thirteen ridges of mountains. - Matthew Everingham, 1795
After these first tentative steps Francis Barrallier, an engineer and explorer who came to Sydney as aide-de-camp to Governor King got approval to explore the mountains. On 5 November 1802 Barrallier, along with four soldiers and five convicts, left Prospect to explore the Blue Mountains. Penetrating about 160 kilometres into the hills he named Byne’s Gap, and the Burragorang valley but was stopped from reaching the Great Dividing Range by a large waterfall. The State Library of New South Wales holds an incomplete extract from Barralier's journal among it's Bank's papers which may refer to this expedition.
A few years later another significant attempt was made by George Caley (1770-1829), who had arrived in Sydney in 1800. Appointed to collect plants for Sir Joseph Banks he took up residence at Parramatta, to the west of Sydney, and from here went on regular excursions into the Blue Mountains. In November 1804 he made an attempt to cross the Blue Mountains which ended at a place he named Mount Banks overlooking the Grose Valley. There is a monument at Linden named after Caley, although it’s not known if he ever actually reached that far west.
I was out three weeks which was as long as I was able to abide for the want of provisions The rough map of the country I found beyond description I can not give you a more expressive idea than travelling over the tops of the houses in a town. - George Caley, 1804 
It seems these traveller's accounts of precipitous cliffs, dead-end canyons and rugged countryside effectively halted official exploration and it would be another decade before a small but well organised party set out to make a determined effort to find a way through the mountains.
Finding a route across the Blue Mountains
On the 28th [May 1813] they proceeded about five miles and three-quarters. Not being able to find water, they did not halt till five o'clock, when they took up their station on the edge of the precipice. To their great satisfaction, they discovered that what they had supposed to be sandy barren land below the mountain, was forest land, covered with good grass and with timber of an inferior quality. In the evening they contrived to get their horses down the mountain by cutting a small trench with a hoe, which kept them from slipping ... - Gregory Blaxland
On Tuesday the 11 May 1813, Gregory Blaxland (1778-1853) struck out with his colleagues William Charles Wentworth (1790-1872) and William Lawson (1774-1850) to find a passage to the western plains. After crossing the Nepean River at Mr. Chapman’s farm at Emu Island they entered the ranges at current Lapstone Creek and started following the line of ridges from there. Even though the distance they travelled on this and on the subsequent days was estimated at about two miles per hour their expedition would prove to be the first to find a crossing over the rugged terrain.
Blaxland had tried earlier to cross the mountains to find new pastures for his sheep and he led the expedition. William Charles Wentworth, the future barrister, author, and statesman, was only 22, but was already Acting Provost Marshall and his youth and adventurous spirit made him an obvious choice for the expedition. The last member of the party was William Lawson, an experienced colonial officer who had trained as a surveyor in England before he sailed to Sydney in 1799.
The challenges they faced included the damp, often foggy and cold climate, the need to find or carry feed for the horses and sometimes having to descend steep gullies for water. In addition they often found their hopes for an apparently promising way forward dashed as they arrived at the foot of impassable cliffs.
After 21 days hacking their way through the wilderness they finally reached the heights of Mount Blaxland. And from there they saw a vast expanse of forest and grass land stretching before them which was rich enough to support the stock of the new colony. Although the party had stopped short of crossing over the mountains Sydneysiders eagerly greeted the news that the explorers had blazed a trail that would show the way through. As Wentworth put it:
Admitting that we have not traversed the Mountains, we have at all events proved that they are traversable and that too, by Cattle - a circumstance….(hitherto) deemed impossible. - William Wentworth
Original journals and notebooks relating to the first crossing of the Blue Mountains
Given the importance of the expedition we are lucky that all three explorers kept journals, leaving behind rich primary source material relating the expedition.
The following day was spent in cutting a passage through the brushwood, for a mile and a half further. They returned to their camp at five o'clock, very much tired and dispirited. The ridge [near Linden Station], which was not more than fifteen or twenty yards over, with deep precipices on each side, was rendered almost impassable by a perpendicular mass of rock, nearly thirty feet high, extending across the whole breadth, with the exception of a small broken rugged track in the centre. By removing a few large stones, they were enabled to pass. - Gregory Blaxland, 1813
Gregory Blaxland published his account as a third person narrative in 1823. Titled A journal of a tour of discovery across the Blue Mountains in New South Wales it was published through B.J. Holdsworth in London. The State library of New South Wales holds three copies of this rare book and one of these have been digitised and made available online. There is also a version of the journal which was transcribed by Frank Walker and published in 1907, this has since been turned into an eBook by Project Gutenberg and this transciption can be freely accessed online.
A country of so singular a description could in my opinion only have been produced by some Mighty convulsion in Nature - Those immense unconnected perpendicular Masses of Mountain which are to be seen towards its Eastern Extremity towering above the Country around, seem to indicate that the whole of this tract has been formed out of the Materials of the primitive mountains of which these masses are the only parts that have withstood the violence of the concussion. - William Wentworth, 1813
William Charles Wentworth kept a small 14 page journal from the 11 May to the 6 June 1813. In it he paints vivid pen portraits of the landscapes, native animals, and the fog and frost they encountered as they traversed the mountains. He also writes about the possibilities for cattle to traverse the mountain pass as this was one of the aims of the expedition: to locate further grazing lands that would encourage settlement beyond the Cumberland Plain. The State Library of New South Wales holds the original copy of this journal and has also made a digitised version available online.
... the mountains very scrubby and rocky, obliged to go for water into a very steep gully abt [about] six hundred feet deep, our horses had no water this night. - William Lawson, 1813
William Lawson kept a notebook which provides accurate records of compass readings, times and distances travelled. In many ways it is a testament to his skill that the first road over the mountains, surveyed by George William Evans and built by William Cox in 1814-1815, closely follows the explorers' original trail. His journal documents the trial and error strategy which they used to find their way through the rugged terrain and Lawson's pride in the endeavour is made clear in his descriptions of vistas previously unseen by Europeans. Lawson later moved stock into the newly opened land and from 1819 to 1824 served as commandant of the new settlement at Bathurst. He later retired to 'Veteran Hall', his home on the land granted to him at Prospect, Western Sydney. He died there in 1850. The State Library of New South Wales holds the original Lawson notebook which includes a wax impression of Lawson's fob seal showing a coat of arms. A digitised version of the notebook has been made available online.
Building a road over the Blue Mountains
Soon after their return the New South Wales the Governor, Lachlan Macquarie, called upon the services of the Tamanian Deputy-Surveyor George William Evans (1775-1852), to investigate Blaxland, Wentworth and Lawson's route with a view to building a road over the mountains. Evans retraced the explorers' trail in November 1813, surveyed the route, and pushed on into the grassy plains beyond the mountains eventually reaching the Macquarie River some 68 kilometres beyond Bathhurst. It is interesting to note that this made Evans the first European to cross the dividing range as Blaxland's expedition had stopped just short of final crossing.
In 1814 Macquarie commissioned William Cox, military officer, roadmaker and builder, to supervise the building of a road across the Blue Mountains, following the route surveyed by George Evans. The State Library of New South Wales holds a series of original papers and journals relating to the lead up to the expedition and the building of the road. And one of these Series 02: William Cox - Journal, 7 July, 1814 - 7 January, 1815 is available online and gives a detailed account of the building of the road, including weather conditions, daily progress, and details about the convict labourers including supplies of clothing and other provisions.
After the successful construction of the road Macquarie and a group of about 50 colonists, including his wife Elizabeth, set out in April 1815 to make the crossing. One member of this group was John William Lewin (1770-1819), a natural history artist and collector, and he recorded the journey in 21 watercolour drawings. Fifteen of these are held in the State Library of New South Wales collections. Another member of the group was Macquarie's aide-de-camp Major Henry Antill (1779-1852) whose 'Journal of an excursion over the Blue or Western Mountains of New South Wales, to visit a tract of new discovered Country in company with His Excellency Governor & Mrs Macquarie, and a Party of Gentlemen' from 25 April-19 May 1815 is also held by the Library and is available online.
Once in the mountains, the party witnessed first hand the challenges the road builders had tackled, as well as the scenic grandeur. Descending into the grassy plains on the western side of the mountains, they camped on the banks of the Macquarie River for a week. It was during this time that the Governor selected a suitable site for the erection of a town to be named Bathurst. The party returned to Sydney on 19 May 1815.
Celebrating the centenary of the crossing
To mark the centenary of the 1813 crossing by Blaxland's expedition historian, writer and lecturer Frank Walker (1861-1948) wrote an official history. Published in 1913 it was titled Cox, W., Blaxland, G., Antill, H., & First Crossing of Blue Mountains Centenary Committee. (1912) and to support his research Walker amassed a large collection of maps, leaflets, brochures and newspaper clippings. Many of these are now in the State Library of New South Wales collection and an album of this material is available online.
 Everingham, Ross, & Ross, Valerie. (1985). The Everingham letterbook / letters of a First Fleet convict / edited by Valerie Ross. Wamberal [N.S.W.]: Anvil Press.
 Barrallier, Francis Louis (1773–1853),by Vivienne Parsons, Australian Dictionary of Biography.
 Barrallier, F. (1975). Journal of the expedition into the interior of New South Wales 1802 : By order of His Excellency Governor Philip Gidley King / by Francis Barrallier. Melbourne: Marsh Walsh.
 Incomplete extract from the journal of Francis Barrallier, November - December 1802, Banks Papers, State Library of New South Wales, SAFE/Banks Papers/Series 35.2, IE3227571.
 Letter to Joseph Banks, George Caley 16 December 1804, State Library of New South Wales.
 This set belonged to Major Henry Colden Antill who had accompanied Lewin and had been given to him in exchange of a copy of the journal he had made of the journey. Blue Mountains, 1815-1816 watercolour drawings by John William Lewin, State Library of New South Wales, PXE 888.
 George William Evans papers, 1802-1852, 1 volume of textual material (unpaged) various sizes manuscript, typescript and newscuttings, Bequeathed by Sir William Dixson, 1952, State Library of New South Wales, DLMSQ 332 , DLMSQ 333
 A. K. Weatherburn, 'Evans, George William (1780–1852)', Australian Dictionary of Biography, National Centre of Biography, Australian National University, http://adb.anu.edu.au/biography/evans-george-william-2029/text2501, published first in hardcopy 1966, accessed online 4 May 2017.
 William Cox - Journal, 7 July, 1814 - 7 January, 1815, SERIES 01 William Cox - Journal, 18 July - 2 December 1814,
C 708/1: diary entries Mon. 18 Jul. - Fri. 2 Dec. 1814, and some preliminary pages giving a narrative account of the origins and conditions of the undertaking.
C 708/1 titled "Narrative of Proceedings by Wm Cox, Esq. of Clarendon in constructing a road from Captn Woodriffe's farm on the Neapean River opposite Emu Plains on the banks of Macquarie River in the year 1814 and 1815". SERIES 02 William Cox - Journal, 7 July - 7 January, 1815,
C 708/2: diary entries 7 July 1814 - 7 January 1815, with 8 additional pages at the end of miscellaneous information, including lists of names, and "Memorandum for watering & feeding stock"; many undated, some upside down, or written sideways.
C 708/2: "Journal kept by Mr Cox in making a road across the Blue Mountains from Emu Plains to a new country discovered by Mr Evans to the westward" -- title page..
Bergman, G., & Blue Mountains Historical Society. (1956). Blue Mountains history in governmental despatches : A survey / by George F.J. Bergman. Katoomba, N.S.W.]: Blue Mountains Historical Society.
Brownscombe, R. (2004). On suspect terrain : Journals of exploration in the Blue Mountains 1795 - 1820 / selected and edited by Ross Brownscombe. Brighton East, Vic.]: Forever Wild Press.
Cox, W. (1901). Memoirs of William Cox, J.P. : Lieutenant and Paymaster of N.S.W. Corps, or 102nd Regiment, late of Clarendon, Windsor / William Cox. Sydney [N.S.W.]: William Brooks, printer.
Houison, J., & Royal Australian Historical Society. (1935). John and Gregory Blaxland / by J.K.S. Houison. Sydney, N.S.W.: S.n.
William Lawson, Journal of an expedition across the Blue Mountains, 11 May - 6 June 1813, together with wax impression of Lawson's seal, State Library of New South Wales, Safe 1/97, Safe 1/97.
Leyden, P., & Curtis, J. (1964). Crossing the blue mountains / written and edited by Peter Leyden ; layout and art by John L. Curtis. (A visual Australian history). Sydney: Peter Leyden Pub.
Low, J. (1990). Crossing the Blue Mountains / Jim Low. (Jacaranda young inquirers). Milton, Qld.: Jacaranda Press.
Turpin, Evans, Turpin, Mary Lempriere, & Evans, George William. (1913). The First crossing of the Blue Mountains, New South Wales, by George William Evans, deputy surveyor general of New South Wales, 30th November 1813 / compiled by his daughter, Mary Lempriere Turpin, nee Evans. Sydney?: S.n.
Walker, F., Cox, W., Blaxland, G., Antill, H., & First Crossing of Blue Mountains Centenary Committee. (1912). The first crossing of the Blue Mountains : [newspaper extracts, manuscript notes, maps, photographs, etc.] / illustrated by Frank Walker. Sydney?: F. Walker,].
Margot Riley and Geoff Barker, Curatorial, Research and Discovery, State Library of New South Wales, 2017