Civic Day is a holiday that is not based on any particular historical or religious event. The intent of the Civic Holiday seems simply to be to "not work".
The tradition of a Canadian holiday in the middle of summer dates back to Toronto in 1869. It was formally created in 1875 when the first Monday in August became the August Civic Holiday in Toronto.
Today, while Civic Day has been adopted as a statutory holiday in other provinces, Civic Holiday is a non-statutory holiday in Ontario.
Federal government offices will be closed, but provincially regulated employers are not required to treat this as a holiday. Despite this status, the holiday is still widely observed across the province.
Colonel By Day
In Ottawa, this day is known as Colonel By Day. It is named after Lieutenant-Colonel John By, an English military engineer, who constructed the Rideau Canal and founded Bytown, which would become the Canadian capital, Ottawa.
By was born on August 7th 1779, which meant the holiday weekend in early August was a suitable date to mark the Colonel's legacy.