In 1827 this explorer, whose industry never flagged, started on the most eventful trip he ever made, destined to considerably affect the immediate progress of the new colony established at Moreton Bay. On the 30th of April he left Segenhoe Station, on the Upper Hunter, and on crossing Oxley's 1818 track to Port Macquarie, at once entered on the unexplored northern region. On the 19th May, after traversing a good deal of unpromising country, a fertile valley was entered, which led the travellers on to the banks of the Gwydir River, one of Cunningham's most important discoveries. He next found and named the Dumaresque River, and finally emerged on the beautiful plateau, thenceforth known as the Darling Downs, where the Condamine River received its name, after the Governor's aide-de-camp. Cunningham's description of this tract of pastoral country is very glowing:-- "Deep ponds, supported by streams from the highlands immediately to the eastward, extend along their central lower flats. The lower grounds thus permanently watered present flats which furnish an almost inexhaustible range of cattle pasture at all seasons of the year; the grass and herbage generally exhibiting in the depth of winter an extreme luxuriance of growth. From these central grounds rise downs of a rich black and dry soil, and very ample surface; and as they furnish abundance of grass and are conveniently watered, yet perfectly beyond the reach of those floods which take place on the flats in a season of rain, they constitute a sound and valuable sheep pasture." Here Cunningham halted for some time, with the view of ascertaining the practicability of a passage across the range to Moreton Bay. In exploring the mountains immediately above the tents of the encampment, a remarkably excavated part of the main range was discovered, which appeared likely to prove available as a pass. Upon examination, the gap was found to be rugged and broken, partially blocked with fallen masses of rocks, and overgrown by scrub and jungle. Beyond these impediments, which could soon be removed, the gap now known as Cunningham's Gap was apparently available as affording a descent to the lower coast lands. Relinquishing any further attempts for the present, either through the mountains or to the western interior, Cunningham returned to the Hunter, crossing and re-crossing his outward track. He was absent oil this expedition thirteen weeks.