In 1828 the Governor of New South Wales, Ralph Darling sent Sturt and Hamilton Hume to explore the area of the Macquarie River in western New South Wales. They discovered and named the Darling River, but were unable to proceed further. This expedition proved that northern New South Wales was not an inland sea, but deepened the mystery of where the western-flowing rivers of New South Wales went to.
In 1829 Governor Darling approved an expedition to solve this mystery. Sturt prooposed to travel down the Murrumbidgee River, whose upper reaches had been seen by the Hume and Hovell expedition. In January 1830 Sturt's party reached the confluence of the Murrumbidgee and a much larger river, which Sturt named the Murray River. It was in fact the same river which Hume and Hovell had crossed further upstream and named the Hume.
Sturt then proceeded down the Murray, until he reached the river's confluence with the Darling. Sturt had now proved that all the western-flowing rivers eventually flowed into the Murray. In February 1830, the party reached a large lake which Sturt called Lake Alexandrina. A few days later, they reached the sea. There they made the disappointing discovery that the mouth of the Murray was a maze of lagoons and sandbars, impassable to shipping.
The party then faced the ordeal of rowing back up the Murray and Murrumbidgee, against the current, in the heat of an Australian summer. Their supplies ran out and when they reached the site of Narrandera in April they were unable to go any further. Sturt sent two men overland in search of supplies and they returned in time to save the party from starvation, but Sturt went blind for some months and never fully recovered his health.
In 1834 Sturt began farming on land granted to him by the New South Wales government near Mittagong. In 1838 he herded cattle overland from Sydney to Adelaide, on the way proving that the Hume and the Murray were the same river. He then settled in South Australia and was appointed Surveyor-General and Registrar-General.
In August 1844 Sturt and a party of 16 set out to explore north-western New South Wales and to advance into central Australia. They passed the site of Broken Hill, but were then stranded for months by the extreme summer conditions near the present site of Milparinka. When the rains eventually came Sturt pressed on into central Australia until they discovered the Simpson Desert, at which point they were unable to go further and turned back to Adelaide.
Sturt later undertook a second expedition to reach the centre of Australia, but his health broke down in the extreme conditions and he was forced to abandon the attempt.
In 1851 Sturt settled to England, where he died in 1869. He is comemmorated by the municipality of Charles Sturt in Adelaide, Charles Sturt University in regional New South Wales, and the Sturt Highway from Mildura to Adelaide.