Although their provisions were failing them, Cunningham remained for some time on the site of his new discovery, fully impressed with the certainty of its immense importance in the future settlement of Australia. Peel's Plains and Canning Downs were named by him, and to the north-west "beyond Peel's Plains an immeasurable extent of flat country met the eye, on which not the slightest eminence could be observed to interrupt the common level, which, in consequence of the very clear state of the atmosphere, could be discerned to a very distant blue line of horizon."
Cunningham's far-seeing mind fathomed the future requirements of such a vast agricultural and pastoral extent of country, and he at once turned his attention to its natural means of communication with its obvious port, Moreton Bay. A lofty range of mountains to the east and north-east seemed to offer a difficult barrier, and he determined upon making a closer inspection. As his horses were recruiting all the time on the luxuriant herbage, he did not so much regret their own scarcity of rations. Finding a beautiful grassy valley which he named Logan Vale, after Captain Logan, the well-known commandant of Moreton Bay, leading to the base of the principal range, he proceeded to make a nearer inspection. After much climbing of successive tiers or ridges, he gained the loftiest point of a main spur, and through some gaps in the main range itself, he was able to overlook portions of the country in the vicinity of Moreton Bay, and even to recognise the cone of Mount Warning. He took particular notice of one gap, and on closer inspection he came to the conclusion that a line of road could be constructed without much difficulty.
Having spent a week on the Downs, and his shortness of provisions and the weakness of his horses preventing any excursion to the western interior, as his intention had been, he set out on his homeward journey on the 18th of June. In order to render his chart of the country traversed as complete as possible, he kept a course about equidistant between the route of his outward journey and the coastal watershed. He reached Segenhoe on the 28th of July, bringing his men and horses back in safety, after one of the most successful and important expeditions on the east coast.
Memorial to Allan Cunningham, Botanical Gardens, Sydney.
In the following year, accompanied by his old companion Fraser, who had been one of Oxley's party on his two inland expeditions, Cunningham proceeded by sea to Moreton Bay, with the intention of starting from the settlement, identifying the gap he had taken particular notice of, and connecting with his former camp on the Downs. In this attempt he was also accompanied by Captain Logan, but they were unsuccessful. Then Cunningham again went from the outpost of Limestone, with three men and two bullocks, and was completely satisfied. A road through this gap on to the Darling Downs was immediately constructed, and used until the introduction of railway communication: the opening was known far and wide as Cunningham's Gap.
In May, 1830, Cunningham went to Norfolk Island. While there he crossed to the little islet adjoining, known as Phillip Island. Having landed with three men, he sent the boat back. That night eleven convicts escaped, seized the boat, and were launching her when they were challenged by a sentry. One of them replied that they were going for Mr. Cunningham, and they got away though they were fired upon. They did go for Mr. Cunningham, and robbed him of his chronometer, pistols, tent, and provisions. Then they sailed away, and were picked up by a whaler, which they seized and finally scuttled. The Government refused to compensate Cunningham for his loss, and he had to replace the instruments himself.
Cunningham left Sydney on the 25th of February, 1831, on a visit to London, where he spent nearly two years at Kew, returning to Sydney on the 12th of February, 1837. He was appointed Colonial Botanist and Superintendent of the Botanic Gardens, but did not retain the position very long, being disgusted to find that supplying Government officials with vegetables was to be a chief part of his duties. He resigned, and after another visit to New Zealand, whence he returned in 1838, so ill was he that he was compelled to decline to accompany Captain Wickham on his survey of the north-west coast. He died of consumption on the 24th of January, 1839, at the cottage in the Botanic Gardens, whither he had been removed for change of air and scene. He was buried in the Devonshire Street cemetery, and on the 25th of May, 1901, his remains were removed to the obelisk in the Botanic Gardens.