The decline of gold mining in Otago did not check the growth of population and prosperity. Between 1867 and 1881 the combined Otago-Southland population grew from 56,000 to 134,000. Land sales boomed and the province received a good share of the Government expenditure on railways in the 1870s. By 1879 Invercargill and Dunedin were linked by Main Trunk railway to Christchurch, and many branch lines, including one to Kingston on Lake Wakatipu, had been constructed on the open plains and downlands by 1880. But the Central Otago railway, victim of local jealousies and Government prevarication, was a distant dream; it did not reach Alexandra until 1906 and Cromwell until 1921.
During the 1870s Otago received 27,000 assisted immigrants under the Vogel scheme – more than any other province, and 29 per cent of the New Zealand total. Immigrants and former miners swelled the labour pool and Dunedin businessmen had invested their gold-rush profits wisely. For several decades the city was the leading manufacturing, commercial, and financial centre in New Zealand. It was also the pioneer centre of the organised labour movement.
Changes in the countryside also reflected the prosperity generated by wool and gold. By 1880 there were closely settled zones of small arable and livestock farms in coastal Otago from the Waitaki River to the Clutha and on the seaward margin of the Southland Plain. These areas had been freeholded, mainly by settlers of modest means, under Otago's unique policy of deferred payment – a feature of provincial legislation that was incorporated in the land laws of New Zealand in the National Land Act of 1877. Inland from the Southland coast and on the downs of North and South Otago, the runholders had used wool profits to buy their land and create huge freehold estates. Some of these were adorned with gracious homesteads set amid ornamental trees and artificial lakes in the manner of the parklands of the British landed gentry. The estates came in for much criticism as barriers to closer settlement, but several experiments, which were to have revolutionary effects on New Zealand agriculture, were carried out on North Otago and Southland estates during the 1870s and 1880s. These included the breeding experiments between long-wooled and Merino sheep which produced the distinctive Corriedale breed, the first experimental shipment of frozen meat from the Totara Estate via Port Chalmers to London 1882, and the application of lime direct to pastures at the New Zealand and Australian Land Co's. Edendale Estate. Furthermore, during the golden age of the estates most of the flat and rolling tussock land was put under the plough, often through the agency of share croppers, and planted in oats, wheat, turnips, and improved pasture. In the 20 years after 1870 land under grain crops in Otago increased from 80,000 to 284,000 acres and the extent of sown pasture from 130,000 acres to 1,200,000 acres. Central Otago remained largely in leasehold sheep runs, but on the margins of the basins and on fertile river flats former miners were turning their sluicing races to irrigate orchards and small farms.
All was not progress, however. In the dry interior hills and mountains, sheep grazing, burning, and the explosive spread of millions of rabbits bared the land of almost all vegetation except the grey unpalatable scabweed. Rabbit carcasses figured prominently in the exports of Dunedin and Bluff – 14 million were shipped in 1894 – but the increase in Otago's sheep flock came to a halt in 1878 and showed no further advance until after 1920.