Municipal associations in Ontario have a long history consisting of numerous amalgamations and mergers of separate organizations.

The first meeting of an enduring municipal association was held in Hamilton on September 6, 1899. The name "Ontario Municipal Association" was chosen, and it was agreed that there would be annual meetings, or "oftener if need be, upon the call of the executive committee", so that both appointed and elected representatives of municipalities could discuss common concerns. A constitution for the organization was drawn up, officers elected and the mandate decided ‑ to establish regular meetings between the association and the government to speak to, and to influence legislation.

The Association of Municipalities of Ontario was created through the merger and reconstitution of the Ontario Municipal Association and the Ontario Association of Mayors and Reeves on June 22, 1972. Further organizational change continued to be discussed in the late 1970s when exploratory meetings were held between AMO and two other major municipal organizations which also existed at that time: The Rural Ontario Municipal Association and The Association of Counties and Regions. Discussions were also held with affiliated associations: The Organization of Small Urban Municipalities (OSUM), The Association of District Municipalities, The Federation of Northern Ontario Municipalities (FONOM), and The Northwestern Ontario Municipal Association (NOMA).

In February 1980, an Association Review Committee was struck and presented its report in June 1980. A new association of municipal representatives was proposed, consisting of five sections, "restructured to ensure accurate representation of the positions of the different types of municipalities in the province". The newly constituted Association of Municipalities of Ontario came into being on January 1, 1982. In May of 1990 AMO became formally incorporated without share capital. AMO's constitution was re‑formulated into governing By‑law No. 1. The By‑law has been amended a number of times to implement significant changes to the Association.
 

AMO Presidents

2016-2018
2014-2016
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2010
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1997-2000
1995-1997
1994/95
1993/94
1992/93
1991/92
1990/91
1989/90
1987/88
1986/87
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1985
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1983/84
1982/83
1981/82
1980/81
1979/80
1978/79
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1975/76
1974/75
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1972/73
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1899
 
Lynn Dollin, Innisfil
Gary McNamara, Tecumseh
Russ Powers, Hamilton
Gary McNamara, Tecumseh
Peter Hume, Ottawa
Norman Sandberg, Collingwood
Peter Hume, Ottawa
Doug Reycraft, Middlesex
Roger Anderson, Durham Region
Ann Mulvale, Oakville
Ken Boshcoff, Thunder Bay
Ann Mulvale, Oakville
Michael Power, Geraldton
Terry Mundell, Erin
Bill Mickle, Exeter
Mabel Dougherty, Onondaga
Joe Mavrinac, Kirkland Lake
Helen Cooper, Kingston
John Harrison, Delhi
Grant Hopcroft, London
Michael Power, Geraldton
Doris Brick, Peterborough
Claudette Millar, Cambridge
Marianne Wilkinson, Kanata
Ron Eddy, South Dumfries
Marlene Catterall, Ottawa
Gerald Parisien, Cornwall
Curtis Carter, Chatham
Robert Rutherford, Owen Sound
Clark Mason, Ajax
Hazel McCallion, Mississauga
Gordon Dean, Stoney Creek
Alfred Judd, Town of Simcoe
Gladys Rolling, East Gwillimbury
Fred Cade, St. Clair Beach
Donald Meston, Waterloo
Pierre Benoit, Ottawa
Russell Scott, Belleville
A. Bedford Ball, Owen Sound
Joseph Fabbro, Sudbury
Garnet Newkirk, Chatham
David J. Low, Fergus
J. A. Heenam, Cobourg
T. J. McKibbin, Kingston
Albert M. Campbell, Scarborough
C. Edgar Norris, Toronto
Georgina Montrose, Windsor
E. C. Reid, St. Thomas
William R. Allen, Toronto
O. W. Larry, Trenton
J. W. C. Langmuir, Brockville
Grace Hartman, Sudbury
S. H. Blake, Fort William
Horace E. Kilman, Pelham
Alan S. Stewart, Owen Sound
V. H. Evans, Tisdale
R. E. Ashton, London
T. H. Currah, St. Thomas
J. F. Berry, Hamilton
M. Anne Shipley, Teck
E. A. Outram, Peterborough
H. H. McFadden, Lindsay
W. W. Gardhouse, York
C. A. Curtis, Kingston
E. J. Campbell, Brantford
W. S. Beaton, Sudbury
H. A. Webster, Windsor
J. Wilfred Spooner, Timmins
W. R. Alley, Lindsay
Martin Rowell, London
C. W. McCrea, Sault Ste. Marie
Henry W. Sturm, Kitchener
Stuart K. Watt, St. Catharines
William Jelly, Leeds and Grenville
J. P. Ryan, Brantford
George Hurst, Toronto
W. L. Wilkinson, Niagara Falls
K. W. McKay, Elgin
Marjorie D. Stewart, Sarnia
Frank J. Mitchell, Windsor
George W. Riseborough, Harwich
C. J. Tulley, Ottawa
J. C. Forman, Toronto
H. James, Fort William
W. H. Nugent, Hastings
W. B. Doherty, St. Thomas
J. F. Vance, Wellington
M. Huenergard, Kitchener
Mary Grant, Township of London
Thomas L. Church, Toronto
Thomas J. Moore, Guelph
Samuel Baker, London
G. K. Dewey, Brockville
S. H. Kent, Hamilton
W. C. Caughell, Yarmouth
A. K. Brunnell, Brantford
Elias Lemon, Owen Sound
J. G. Richter, London
George H. Lees, Hamilton
F. S. Spence, Ottawa
Charles Hopewell, Ottawa
George Geddes, St. Thomas
M. Kennedy, Owen Sound
W. C. Mickel, Belleville
J. A. Ellis, Ottawa
W. P. Hubbard, Toronto
W. A. Boys, Barrie
John Kennedy, Guelph
R. P. Slater, Niagara Falls
E. J. Reynolds, Brockville
M. Y. Keating, St. Catharines
Hon. Justice J. V. Teetzel, Hamilton