ɪt wʌz kɹiːˈeɪɾᵻd ˌɔn dʒˈuːn twˈɛnti tˈuː, nˈaɪntiːnhˈʌndɹɪd sˈɛvənti tˈuː θɹuː ɐ mˈɜːdʒɚɹ ʌvðɪ ɑːntˈæɹɪˌoʊ mjuːnˈɪsɪpəl ɐsˌoʊsɪˈeɪʃən ænd ðɪ ɑːntˈæɹɪˌoʊ ɐsˌoʊsɪˈeɪʃən ʌv mˈeɪɚz ænd ɹˈiːvz.
It was created on June 22, 1972 through a merger of the Ontario Municipal Association and the Ontario Association of Mayors and Reeves.