Though street signs and the official city plan now show the spelling as "McKenzie," this is an error which crept in remained through the years.
A factor that may have led to the change in the spelling was the confusion that arose in the early 1870s when Stratford had a second Mackenzie Street, named in honour of Alexander Mackenzie, the second Prime Minister of Canada. It was later changed to McKenzie Street.
William Mackenzie was a land developer who lived in Galt. He was probably a man of some means and influence who had access to information about the proposed location of the Grand Trunk Railway operation in Stratford.
Two of his three land development projects here were adjacent to the Grand Trunk railway line. He bought the land in 1853 in anticipation of the coming of the railway (in 1856) and McKenzie Street was built up during the railway boom.
When the Grand Trunk locomotive repair shops moved to Stratford in 1870-71, McKenzie Street received another boost. At the peak of the steam locomotion era, more than 2,000 people working for the GTR in Stratford, many of them wanting houses close to the railway operation. Source: Streets of Stratford 2004