1873

The first Public Health Act was passed.

1882

The first board of health was established.

1884

A more comprehensive Public Health Act was prepared by Dr. Peter H. Bryce. This Act established the position of the Secretary of the Board of Health (now called the medical officer of health) and the relationship with the board of health. Within two years of passage, 400 boards of health were in operation.

1912

The Public Health Act was amended so that health units could be established on a county basis.

1934

The first county-wide health unit was established with a grant from the Rockefeller Foundation. It included the four eastern counties of Stormont, Dundas, Glengarry, and Prescott. At this time, Ontario had 800 local boards of health and 700 medical officers of health, most of whom were part-time.

1945

The Public Health Act was amended so that provincial grants could be provided to municipalities for the establishment of health units. Six health units were in place by the end of 1945.

1950

Twenty-five county and 12 municipal health units were in place which served two thirds of the population of Ontario.

1965

Fifty-four boards of health were in place, which served 95 percent of the population.

1967

The Public Health Act was amended so that organized municipalities were required to provide full-time public health services. The District health unit concept was introduced based on the collective experience of operating health units in Ontario. Economies of scale concepts were introduced which suggested optimum population sizes (100,000) for health unit catchment areas. The province encouraged health units to regroup on a multi-county basis to become more efficient.

1983

The Health Protection and Promotion Act (HPPA) was proclaimed, replacing the Public Health Act. The Act was amended in 1990 making slight changes to its contents.

1997

The HPPA was revised as part of Bill 152, the Services Improvement Act. Mandatory Health Programs and Services Guidelines published.

1998

The former Metropolitan Toronto was amalgamated into a single City of Toronto. Six former public health departments in the boroughs of East York, Etobicoke, North York, Scarborough, York and the city of Toronto merged into a single entity, i.e. Toronto Public Health. This amalgamation reduced the total number of public health units in Ontario from 42 to 37.

2005

Following recommendations by assessor Graham Scott, the Muskoka-Parry Sound Board of Health was dissolved and merged with two other health units (the then-Simcoe County District Health Unit and then-North Bay District Health Unit). This action reduced the overall number of public health units in Ontario from 37 to 36.

2007

The Ontario Agency for Health Protection and Promotion is established in Toronto.

2008

The Ontario Public Health Standards are completed in collaboration with boards of health and Ontario public health professionals. They came into effect on January 1, 2009, replacing the Mandatory Health Programs and Services Guidelines.

2010

The Ontario Agency for Health Protection and Promotion changes its operational name to Public Health Ontario.

 The Patients First Act includes a clause that formalizes engagement between the local Medical Officer of Health and LHIN CEOs on issues related to local health system planning, funding and service delivery.