1615: First Mass in Huronia is held on the southern shores of Georgian Bay.
1640s: Jesuit priests are martyred in Huronia.
1767: First Catholic parish in Ontario for Europeans is established in Windsor.
1780s: Catholics from Scotland settle in Stormont and Glengarry counties.
1790s: Right Reverend Edmund Burke, Vicar-General for Upper Canada, purchases parcels of land for future sites of Catholic churches and institutions.
1793: York is founded with the arrival of John Graves Simcoe.
1806 Catholic settlers in Ontario number about 170.*
*ARCAT, Bishop Macdonell Fonds, M CG01.02, letter from Rev. Alexander Macdonell to Bishop Plessis, May 10, 1806.
1812-1815: War of 1812
1822: St. Paul's Church, the first Roman Catholic parish in Toronto, is established.
1826: Upper Canada is transferred from the jurisdiction of the Bishop of Québec to the new Bishop of Kingston, Alexander Macdonell.
1837-1838: Upper and Lower Canada Rebellions
1841 December 17: The Diocese of Toronto is created, encompassing the western half of Upper Canada. Michael Power is appointed its first bishop.
1842 June 26: Bishop Power is installed at St. Paul's Church in Toronto.
1842 October 6-8: First Toronto diocesan synod is held to establish the policies and regulations to govern the new diocese and its 25,000 Catholics.*
* From Censuses of Canada, 1665-1871, vol. 4 of Census of Canada, 1870-1871 (Ottawa: I.B. Taylor, 1876) and Documentary History of Education in Upper Canada, ed. J.G. Hodgins (Toronto: L.K. Cameron, 1900). See Appendix 3 of Mark G. McGowan’s Michael Power: The Struggle to Build the Catholic Church on the Canadian Frontier (Montreal and Kingston: McGill-Queen’s University Press, 2005).
1845 March 29: The Diocese of Toronto is incorporated as the Roman Catholic Episcopal Corporation for the Diocese of Toronto, in Canada. See Statutes of the Province of Canada, 1845. An Act to Incorporate the Roman Catholic Bishops of Toronto and Kingston, in Canada, in each Diocese (pp. 499-502).
1845 May 8: Bishop Power lays the cornerstone of St. Michael's Cathedral.
1846 December 7: St. Michael’s Palace (Episcopal Residence, Chancery Office and Cathedral Rectory) is blessed.
1847 October 1: Bishop Power dies and is buried beneath the unfinished cathedral.
1848 September 29: St. Michael’s Cathedral is consecrated by Bishop Bourget of Montréal. The Catholic population reaches 50,000.
1850 September 22: Bishop Armand-François-Marie de Charbonnel is installed as the second bishop of Toronto. He uses his personal estate to pay off debt on St. Michael's Cathedral.
1852: St. Michael's College is founded at the University of Toronto.
1855: St. Michael's Cemetery is founded to serve all of the downtown parishes in York.
1856: The Diocese of Toronto is divided by the erection of the dioceses of Hamilton and London.
1857: House of Providence opens.
St. Paul’s Church Cemetery is officially closed. The cemetery filled up quickly with the burials of Irish immigrants who had succumbed to typhus following their escape from the Great Famine.
1858: Bishop de Charbonnel imports St. Michael’s Cathedral’s three east windows and the Stations of the Cross from France.
1859 August 16: Bishop John J. Lynch is appointed coadjutor to Bishop de Charbonnel.
1860 April 29: Bishop de Charbonnel resigns and returns to France. Bishop Lynch becomes the third Bishop of Toronto.
1863: Bishop Lynch holds a diocesan synod to solidify the regulations governing the 40,000 Catholics in his care.*
* The Metropolitan Catholic Almanac and Laity’s Directory for the United States, Canada, and the British Provinces (Baltimore: John Murphy and Co., 1861), p. 246.
1867 July 1: The Dominion of Canada is established through the British North America Act.
1870 March 18: Pope Pius IX raises Toronto to an Archdiocese during Vatican Council I, making Bishop Lynch an Archbishop.
1873: St. Michael's Cathedral is completed with the addition of the tower, steeple, sacristy, bells and fence.
1875: The Jubilee Riots in Toronto
1876: Sacred Heart Orphanage, also known as "Sunnyside", is established on the site of today's St. Joseph's Health Care Centre.
1877: Archbishop Lynch establishes a seminary in St. John's Grove (located on the property of Our Lady of Lourdes Parish).1879 Auxiliary Bishop Timothy O'Mahony is appointed to the Archdiocese of Toronto and takes up residence at St. Paul's Parish.
1886: Catholic population is 57,000.*
* ARCAT, Letterbooks, LB05.043, Statistical Report, October 16, 1886.
1887 October 9: Cornerstone of the new St. Paul’s Church is laid.
1888 May 12: Archbishop Lynch dies and is buried in the garden of St. Michael's Cathedral.
1889 November: Archbishop John Walsh is installed in Toronto.
1891 March 29: Bishop de Charbonnel dies a Capuchin friar in France.
1891 June 7: Archbishop Walsh blesses St. John's Chapel, an addition to St. Michael’s Cathedral.
1892: St. Michael’s Hospital is founded by the Sisters of St. Joseph.
1893: The Catholic Register newspaper is started by the Archdiocese of Toronto.
1898 July 30: Archbishop Walsh dies and is buried in front of the altar of the Blessed Virgin Mary in St. Michael's Cathedral.
1899: Catholic population is 65,000, served by 85 parishes and missions.*
*Hoffmann’s Catholic Directory (Milwaukee: Hoffman Company, 1899), p. 43.
1899 May 3: Archbishop Denis O’Connor, CSB is installed in Toronto.
1900: Mount Hope Cemetery is opened.
1908 April 13: Bishop Fergus Patrick McEvay is appointed Archbishop of Toronto.
1908 May 4: Archbishop O’Connor resigns.
Canadian Catholic Church Extension Society is founded [name changes to Catholic Missions in Canada in 1999].
1910 October 23: Cornerstone of St. Augustine's Seminary is laid.
1911: Catholic population is 70,000 and Archbishop McEvay has created seven new parishes, bringing the total number of churches to 92; he has also built 10 church buildings and a new archiepiscopal residence.*
*Catholic Directory, Almanac and Clergy List (Milwaukee: Wiltzius Company, 1911), p. 55.
1911 May 10: Archbishop McEvay dies and is buried in Regina Cleri Cemetery at St. Augustine’s Seminary
1911 June 30: Archbishop O'Connor dies and is buried at Mount Hope Cemetery.
1912 December 22: Archbishop Neil McNeil arrives in the Archdiocese of Toronto.
1913: Catholic Charities Office is formed [name changes: Federation of Catholic Charities (1927); Council of Catholic Charities (1946); Catholic Charities of the Archdiocese of Toronto (1981)
1913 August 28: Opening of St. Augustine's Seminary.
1914 August 4: Canadian Governor General declares war on Germany
1917: Catholic population is 75,000, served by 100 parishes and missions.*
*The Ontario Catholic Year Book and Directory (Toronto: Newman Club Toronto, 1918), p. 40.
1918 November 11: Armistice is signed ending World War I.
1924: China Mission Seminary is established next to St. Augustine's Seminary, later becoming the Scarborough Foreign Mission Society.
1929: Catholic population is 125,000, served by 119 parishes and missions.*
*The Official Catholic Directory Anno Domini 1929 (New York: P.J. Kennedy and Sons, 1929), p. 61.
1929 September: Foundation of the Institute of Mediaeval Studies [is created a Pontifical Institute in October 1939].
1929 October 29: Stock market crashes marking the beginning of Great Depression
1934 May 25: Archbishop McNeil dies and is buried at St. Augustine's Seminary.
Catholic population is 165,000* and the number of parishes and missions has grown to 126.**
*The Official Catholic Directory Anno Domini 1935 (New York: P.J. Kennedy and Sons, 1935), p. 47.
**Hoffmann’s Catholic Directory (Milwaukee: Hoffman Company, 1899), p. 43.
1935 Mar 20: Archbishop James C. McGuigan is installed in Toronto. Under his administration, the following Auxiliary Bishops are appointed: Benjamin Webster (1946-1954); Francis Allen (1954-1977); Francis Marrocco (1955-1968).
1937: St. Michael’s Choir School is founded.
1939-45 World War II: Archbishop McGuigan releases priests to serve as chaplains in the armed forces and forms a unit of ninety women's societies sending parcels overseas, providing chapels and reading rooms in military camps and serving meals.
Archbishop McGuigan’s administration conducts many successful fund-raising campaigns, including ones for St. Augustine's Seminary and for Catholic education.
1946 February 18: Archbishop McGuigan is elevated to the Sacred College of Cardinals, becoming the first English-speaking Cardinal in Canada.
1947 June 18-22: Marian Congress in Ottawa is presided over by Cardinal McGuigan as the special representative of Pope Pius XII.
1949: Catholic population is 197,000, served by 158 parishes and missions.*
*Le Canada Ecclésiastique: Annuaire du Clergé 1949 (Montréal: Librairie Beauchemin, 1949) p. 388.
1954: Opening of Holy Cross Cemetery in Thornhill.
1958 November: Establishment of the Diocese of St. Catharines.
1959: Catholic population is 365,000, served by 153 parishes and missions.*
*ARCAT, Diocesan Quinquennial Reports, 1959.
1961 February 18: Archbishop Philip F. Pocock is named Coadjutor to the Archbishop of Toronto and takes over the administration of the Archdiocese. Under his administration, the following Auxiliary Bishops are appointed: Thomas Fulton (1968-1978); Aloysius Ambrozic (1976-1990).
1962-1965: The Second Vatican Council (Vatican II) is held in Rome. 
1966: Senate of Priests is established.
1969 January: Archdiocesan Pastoral Council is established.
1970 April: Toronto School of Theology is incorporated.
1971: Cardinal McGuigan resigns.
1973: Catholic population is 750,000, served by 203 parishes and missions.*
*ARCAT, Diocesan Quinquennial Reports, 1973.
1974 April 8: Cardinal McGuigan dies and is buried at St. Augustine's Seminary.
1974 May-June: The first 26 Permanent Deacons of the Archdiocese of Toronto are ordained in five separate ceremonies by Archbishop Pocock.
1976: ShareLife is established when Archbishop Pocock withdraws the Council of Catholic Charities from the United Way.
1978: By 1978 the Catholic population is 900,000 and 45 new parishes had been built for a total of 210 parishes and missions.*
*Canadian Conference of Catholic Bishops Directory 1979 (Ottawa: Concacan Inc., 1979), p. 78.
1978 April 29: Archbishop Pocock resigns.
1978 June 5: Bishop Gerald Emmett Carter is installed as Archbishop of Toronto. Under his administration, the following Auxiliary Bishops are appointed: Robert Clune (1979-1997); M. Pearse Lacey (1979-1993); Leonard Wall (1979-1992).
1979 May 26: Archbishop Carter is elevated to the Sacred College of Cardinals.
1981: Cardinal Carter begins the annual Cardinal’s Dinner.
1982: Covenant House is established in downtown Toronto.
1984: Catholic population is 1,214,000, served by 214 parishes, missions and chapels.*
*Canadian Catholic Church Directory 1985-1986 (Montréal: B.M. Advertising Inc., 1985), p. 218.
1984 September 6: Archbishop Pocock dies and is buried at Holy Cross Cemetery, Thornhill.
1984 September 14-15: Pope John Paul II visits various parts of the archdiocese as part of a pastoral visit to Canada.
1986 May 22: Bishop Ambrozic is appointed Coadjutor Archbishop.
1987: Ontario Government passes legislation providing full funding to Catholic high schools.
Cardinal Carter celebrates a triple anniversary: 75th birthday; 50th year as a priest; and 25th year as a bishop.
1990 March 17: Cardinal Carter resigns, making Archbishop Ambrozic the new ordinary of the Archdiocese of Toronto. Under Archbishop Ambrozic’s administration, the following Auxiliary Bishops are appointed: Nicola De Angelis, C.F.I.C.(1992- 2003); John Knight (1992-2001); Terrence Prendergast, S.J. (1995-1998); R. Anthony Meagher (1997-2002); John Boissonneau (2001- Present); Richard Grecco (2002-2009); Daniel Bohan (2003-2005); Peter J. Hundt (2006-2011).
1991 April: Archbishop Ambrozic announces the creation of an office of youth ministry [now called Office of Catholic Youth].
1992: Catholic population is 1,337,000,* served by 233 parishes, missions and chapels.**
*Canadian Catholic Church Directory 1985-1986 (Montréal: B.M. Advertising Inc., 1985), p. 218.
**ARCAT, Diocesan Quinquennial Reports, 1992.
1998 February 21: Archbishop Ambrozic is elevated to the Sacred College of Cardinals.
2000: Year of the Great Jubilee celebrating the third Christian millennium.
2000 November 5: Official Blessing of St. Paul's Church as a Minor Basilica.
2002 July 23-28: World Youth Day in Toronto, presided over by Pope John Paul II.
2002 November 16: Canadian Catholic Bioethics Institute (CCBI) is officially opened.
2003 April 6: Cardinal Carter dies and is buried at Holy Cross Cemetery, Thornhill.
2005 April: Cardinal Ambrozic attends the conclave which elects Pope Benedict XVI.
2006 December 16: Pope Benedict XVI accepts the resignation of Cardinal Ambrozic and appoints Archbishop Thomas Christopher Collins as the tenth Archbishop of Toronto. Under his administration, the following Auxiliary Bishops are appointed: William McGrattan (2010-2014); Vincent Nguyen (2010-Present); Wayne Kirkpatrick (2012-2019); Robert Kasun, CSB (2016-Present); Ivan Camilleri (2020-Present)
2012 February 18: Archbishop Collins is elevated to the Sacred College of Cardinals.
2013 February 11: Pope Benedict XVI announces his resignation for the end of the month, becoming the first pope to resign since 1415.
2020 March: COVID-19 is declared a global pandemic. On March 17th, the Premier of Ontario declares a state of emergency and Cardinal Collins cancels all public Masses to support public health efforts to stop the spread of the coronavirus.
2023 February 11: Pope Francis accepts the resignation of Cardinal Thomas Collins and appoints Auxiliary Bishop of Montreal Francis Leo as the eleventh Archbishop of Toronto.