In 1875 or late 1874 Captain Alexander McCoy conceived the idea for a new steamship company on the Adelaide to Melbourne run. With the agreement of other Adelaide businessmen a proposal was made to float shares for the Adelaide Steamship Company (ASC). The first ship of the new company was the Flinders, 521 ton, with accommodation for 112 passengers, built at Sunderland during 1874 and arriving Adelaide March 1875. Flinders had been built for the Spencer's Gulf Steamship Company but was placed on the ASC's Melbourne run when she arrived from the builders (the businessmen behind Spencer's Gulf SS Company were also involved in the new Adelaide Steamship Company.) The Flinders was subsequently placed into the Spencer Gulf trade for which it had been intended, but in 1882 Spencer's Gulf SS Company amalgamated with ASC which thereby obtained Flinders and Franklin, another new steamer purchased by the latter company.
A rate war ensued with McMeckan Blackwood of Melbourne which was already supplying a regular run to Adelaide: passengers on the run were the only ones to benefit from this. A deal was eventually struck between the two companies, with McMeckan Blackwood continuing to service the intermediate (mainly South East of South Australia) ports. ASC wanted to get into the South East trade, but had to fight off more competition from Melbourne firms, William Howard Smith & Sons, and Nipper & See. After threatening Howard Smith's Melbourne to Sydney run, peace was made with a complex agreement about bunker coal and agents. Nipper & See were more difficult to deal with and ASC directors even considered selling out. Eventually the matter was resolved, with ASC buying the Claude Hamilton and agreeing not to compete against Nipper & See. ASC now turned its attention to the South East trade, and also planned services to Western Australia and New South Wales. By end of 1882 ASC had bought out William Whinham, acquiring three additional steamships, in addition to the already mentioned acquisition of the Spencer's Gulf Steamship Company which included the 605 ton Investigator still being built in the UK. With the acquisition of Spencer Gulf Steamship Company, Adelaide Steamship Company gained six ships for 90,000 pounds. They now had complete domination of the Spencer Gulf, South East and Melbourne steamship trade.
These additional ships could be deployed into the Western Australian trade, or anywhere else: Adelaide Steamship Company had plenty of options. They now bought out Anderson & Marshall and secured a foothold in Western Australia with two additional steamers and three coal hulks, and a ketch tender and company moorings in two ports. The ASC's services now ranged from Melbourne around the southern coast to northern Western Australia.
There was still opposition from other shipowners and overseas lines, and Adelaide Steamship Company also pursued the Darwin mail contract, which they considered theirs by right. The South Australian Post Office disagreed.
Expansion in Western Australia meant that the ASC's resources were stretched - there were never enough ships to blanket the competition, which seemed to be the important thing. Much juggling of ships occurred. A price war with the ketch trade, which Adelaide Steamship Company had no chance of winning was narrowly averted. A new company, Yorke's Peninsula Steamship Company, undercut them in the Gulf trade, and John Darling tried to seize a portion of the Gulf trade as well. Despite local squabbles the Western Australian trade developed with the discovery of gold - first in the Northern Territory, then the Kimberley, Pilbara and finally the Coolgardie-Kalgoorlie fields. Initially Adelaide Steamship Company was the only company operating to these fields, but such a monopoly could not and did not continue. However there was plenty of trade for all, including for the overseas lines, and by the end of 1899 territorial rights and the regulation of freight rates and passenger fares would be hammered out by the shipping industry.