In 1871 another factory was built further south on Gawler place, in the old (1841) Congregational chapel, once the home of J. L. Young's Adelaide Educational Institution. In 1876 they purchased a section on the corner of Pirie Street and Gawler Place. In 1894 vacant land in Wakefield Street was purchased from C. G. Everard for another factory, which later occupied . Simpson was a director and major shareholder in the short-lived "SA Iron and Steel Company", formed in response to a Government incentive, to mine and smelt iron ore at Mount Jagged on Maslin's property near Victor Harbor. Some ore was smelted in 1874 and exhibited at the Show that year, but after a solid plug of smelted iron formed at the base of the furnace the project was abandoned. Other directors were J. Acraman, A. Sidney Clark and J. G. Ramsay. For 49 years he held the reins as proprietor, and then passed most of the responsibilities onto his sons A. A. Simpson and F. N. Simpson, though retaining the role of managing director until his death. He continued to make visits to the company's head office in Gawler Place, and factories in Pirie street and Wakefield street. Simpson, first and foremost a business man, was reluctant to enter Parliament, but in 1887 (South Australia's jubilee year) he consented to contest a vacancy for the Central Division of the Legislative Council on behalf of the Protectionist Party. He signed the nomination paper on the Wednesday prior to the election, and did not address a single meeting, yet was returned at the head of the poll, as a colleague of J. H. Angas, also a Protectionist. He occupied the seat until 1894, then refused to nominate for the following election. He was a level-headed, straight politician of pronounced views. He not only opposed the introduction of payment of members, but, when that measure was carried, he gave the whole of his parliamentary allowance (£1,200) to be used as prize money for the encouragement of rifle shooting. He suffered for a long time from defective eyesight, and died after some years suffering "a serious internal complaint", i.e. cancer. A sister, Catherine Simpson ( – 1 May 1917), married John Crawford Woods on 4 January 1882.