John Baker was born on 28 December 1813 in England. After migrating to Tasmania, and marrying Isabella Allen there he arrived in South Australia in 1838. Within a short time he had opened a store in Hindley Street and bought large parcels of land. He also entered into an agreement with the South Australian Company to import 10,000 sheep from Tasmania which established his first connection with the pastoral industry.
In the 1840s he was listed as director of several mining companies including the Montacute, Paringa, North Kapunda, Adelaide and the Australian Mining Company. Early in 1850 he was one of the directors of the Britannia Mining Company which was going to work seven thousand acres of the Special Mineral Survey on the Bremer River. Baker was very concerned about the shortage of miners in the colony and together with G. Phillips, informed the government in April 1844 'that the number of miners were not adequate to supply the demand'. They wanted to know if it was possible to introduce miners as assisted immigrants. By 1850 Baker had made enough money from whaling, and speculation, to afford to enter politics and the buying of land near Mannum, and the leasing of large properties. He took up pastoral leases, among them Angepena and Blanchewater, and became heavily involved in the mining industry.
Baker had a great deal of experience with the financial aspects of mining ventures. Later Baker became part-owner of leases which were sold to the tune of $140,000 to the Great Northern Copper Mining Company of South Australia which was in the process of being formed and incorporated and would operate the Nuccaleena mine. This company's capital was fixed at $320,000 in 80,000 shares of $4 each. The company's London directors were Charles Bonney, Joseph Turnley, Alfred Wilson, Francis Cope, Charles Cleve and George Hay Donaldson. The last three gentlemen were already on the board of the North Rhine Copper Company. Early in November 1859, a prospectus of the Great Northern Copper Mining Company of South Australia was published in the English Newspapers.
Immediately a great rush for their shares followed. In fact the rush was so great that the subscription list had to be closed almost 'as soon as it opened'. John Baker had acquired 7,125 shares. Newspapers were proud to report that. 'All interested in the progress of South Australia will rejoice to perceive that another step has been made towards the development of her undoubted mineral wealth'.
Baker also became a director of the Bank of Australasia. This bank handled the government accounts and investment money from other colonies in South Australia. In 1851 the Legislative Council was established in South Australia and in August of that year John Baker MLC presented a petition from 46 members of the Church of England in support of government aid for Religion.
Baker was a strong supporter of the Volunteer Movement. At the outbreak of the Crimean War in 1854 he was instrumental in the organisation of the Mounted Rifles. In the same year he applied for the Angepena and Pernunna leases. In 1857 he stocked the Blanchewater run with cattle and even found time to become Premier of South Australia for nine days at the end of August 1857. Baker took a keen interest in horses and racing and was for several years on the committee of the SAJC. One of his horses won the Melbourne Cup in 1873. At his estate at Morialta he produced wine and in 1860 sold more than 30,000 litres. In 1864 he became Captain of the Volunteer Military Force.
Baker was a Special Magistrate, a prominent parishioner and benefactor of the Anglican Church near his home at Morialta. Having made large sums of money from whaling, mining and speculating in land and pastoral properties he lived in comfort on his estate where he died in 1872, aged 59, leaving everything to his wife.
After his death, Henry Ayers said in the Legislative Council that during his whole Parliamentary career 'Baker had proved himself to be a most devoted, earnest and careful legislator, who made himself thoroughly acquainted with every subject that came under his notice'. He also said that 'it would take many years before the Council would have among its members one possessing more zeal, energy and ability than Baker whose loss they all deplored'.