A merchant who became a lawyer, a confidant of the Six Nations, and founder of Galt, William Dickson was one of three brothers brought from Dumfries in Scotland to Niagara by Robert Hamilton, their cousin. Like his brothers, Robert and Thomas, before him, William served an apprenticeship with the firm of Hamilton and Cartwright. Part of William's apprenticeship was spent on Carleton Island, near Kingston, as a forwarding agent under Richard Cartwright, and part was spent as manager of Hamilton's mills and store at Twelve Mile Creek (St Catharines).

After the apprenticeship, Hamilton set Dickson up in his own business, dealing with the military and trading along the new Portage Road on the west side of the Niagara River. Dickson was so successful that, in 1790, at the age of 21, he was able to build the first brick house on the Niagara Peninsula. He became a land speculator and, as a result, got involved with land agency and so gravitated into law. By 1795, he was acting for Richard Beasley and James Secord, Cartwright's cousin and brother-in-law. In 1803, Robert Hamilton arranged for Dickson to become a lawyer even though he had not gone through the usual training.

As a lawyer, Dickson acted for the Six Nations in many of their transactions to sell the blocks of land on the Grand River. In 1811, with his cousin Thomas Clark, he bought Block 1 (Dumfries Township) and five years later Clark sold his portion to Dickson for about a dollar an acre. At that time, Dickson was Chairman of the Quarter Sessions of Niagara and was concerned with building a new courthouse. For the job, he interviewed Absalom Shade, a young builder with ambition and business acumen. Shade made such a good impression that Dickson asked Shade to accompany him on a tour of his new property. Where Mill Creek joins the Grand River, they stopped for a night at an abandoned squatter's cabin. Dickson decided that this area was to be the site for his planned community, first called Shade's Mills and later Galt.

The first industry in Dumfries Township was a gristmill built for Dickson by Shade and later bought by Shade. It was located at Mill Street in Galt. By 1817, the population of the township was about 160 people. To increase settlement, Dickson sent John Telfer to Scotland to encourage more people to come to Dumfries Township and by 1832 every plot was filled, mostly by Scots.