The streets in this area were originally laid out to provide access to the two main mills that were located south of Highway 7 – Markham Mills and Glen Rouge Mill.
The Milne family operated wool and flour mills from 1824 when Peter Milne acquired the property. Peter had no milling experience -- he ran a general store. His brother Alexander ran the woollen and flour mills. When Alexander married and set up his own mills at the corner of what is now Lawrence Avenue and Leslie Street (Edwards Gardens) in Toronto, Peter hired millers to run his site. Peter died in 1845, leaving his wife Elizabeth and their oldest son, Thomas, to manage the operation.
In 1866, a fire caused severe damage to the mills. Only the grist mill was rebuilt, later to be operated by Thomas Milne’s sons, Grant and Archie, under the name Milne Brothers. In the early 1900s, the brothers manufactured a breakfast cereal called Wheateen.
Archie built a steel and concrete arc dam in 1911 to generate power for the growing village. It was the first of its kind in the area. Its embankments were washed out by Hurricane Hazel in 1954.
Today, this area west of Main Street South is known as Milne Park.
To the east of Main Street South, there was another grist mill operated by Archibald Barker.
Barker sold the mill in January 1857. There were a number of owners with full or half interest in the mill throughout the 19th century. Glen Rouge Mill was demolished around 1920. The site is now a conservation area.
While there are many colourful theories on the origin of the name, the most likely explanation is that the steep incline of Main Street South was named Vinegar Hill or Vinegar Dip after a cider mill was constructed on the east side of the valley.