The Township of Thornbury was incorporated on April 23, 1833. The source of its name is somewhat controversial. Some historians claim it was inspired by the wild thorn berries that grew along the Georgian Bay shoreline. Others deduce that the settlement was named after three Thornburys from England.

In 1855, the town's first business, a milling operation was set up. By 1857, the population had reached the 100-person mark. Back then a walk through town would have taken you past a general store, blacksmith, cooper and fanning mill shops, grist and saw mills and a post office. Over the next thirty years, Thornbury continued to grow. The population was now over 1,200 people, and the town had clearly evolved from a spec in the middle of nowhere to a "modern" town with all the places of business, churches, manufacturing facilities and banking institutions found in any other town in Ontario.

Business has always played a major role in the evolution of Thornbury.

Back in 1887, feeling they were unfairly burdened with high taxes, the businessmen of Thornbury petitioned for independence from the Town of Collingwood. After much negotiating, they received it, and the Township of Thornbury became of the Town of Thornbury.

Over the years Thornbury has been home to a wide spectrum of businesses. From the Chemical Works to T.G. Idle's Furniture store which furnished many of the distinguished homes in the area; to the Thos. W. Eastland department store where groceries were displayed on one side and dry goods on the other Keast Tailoring which is still going strong four generations later. The apple packing industry took root in Thornbury in the 1880s. In 1905 the Georgian Bay Fruit Growers Association was formed. The Mitchell family were prominent and vocal members of the group, and for years famous Mitchell-brand cider vinegar, apple juice and sauce were produced in the Thornbury processing plant.

Today the entrepreneurial spirit is alive and well in Thornbury, with Bruce Street still bustling with an eclectic mix of shops, restaurants and artisans.