1865
Trinity College School opened its doors in a rectory in Weston, home of the founder, William A. Johnson. Father Johnson acted as warden and Charles A. Badgely was appointed headmaster. Nine students, all boys, were enrolled, including Father Johnson's three sons.

1868
Because of ever increasing enrolment, TCS moved to its present site (the former Ward Homestead) in Port Hope. Three years' rent on the property was paid by a committee of people from town who were eager to have TCS locate in their midst.

1870
The Reverend C.J.S. Bethune was appointed headmaster, having said some years earlier, "To be a school master is the last thing that I should care to undertake." Apparently his father, the Lord Bishop of Toronto, told him it was his duty to accept the position. Dr. Bethune remained at TCS for 29 years.

1871
The first annual cricket match was played with Upper Canada College. The two schools had played together in 1868, but it was not until 1871 that the yearly competition was established. It has now become the oldest annual competition in Canada.

1872
A dormitory and classroom building were completed.

1874
A chapel was built, parts of which are still intact today despite two fires.

1882
The headmaster's residence, The Lodge, was completed. Designed by renowned architect Frank Darling, it has the distinction of being the oldest intact building on campus.

1886
The Old Boys' Association was organized by a group of four TCS alumni. The first association dinner was held at Walker House, Toronto, on December 17, 1886.

1891
In an effort to relieve the load of duties and responsibilities on Dr. Bethune, the Reverend Arthur Lloyd was appointed headmaster responsible for the academic administration of the School. Dr. Bethune became the warden in charge of the financial side of the School's operations and he continued to live at The Lodge. This new system of administration did not work, however. Father Lloyd resigned after two years and Dr. Bethune once again took full responsibility of the School.

1892
Under the sponsorship of Father Lloyd, the first School magazine, the Red and Black, was published.

1895
In February, an explosion of a coal oil lamp in one of the master's rooms started a fire which destroyed the School. No one was injured, the boys were housed in town and by October of the same year the new set of School buildings was opened.

1896
The Oxford Cup race (still run today) was established by four alumni, all undergraduates from Oxford, who wished to stimulate healthy rivalry between the flats (houses), to encourage running and to assist football by offering a special inducement to train.

1898
The first issue of The Record was published, February 25th. The editor and organizing force behind its publication was Mr. E.M. Watson, head of the classics department.

1899
Dr. Bethune retired and the Reverend R. Edmond Jones was appointed headmaster. Two years later he resigned.

1901
The Reverend Herbert Symonds became headmaster; his tenure lasted only two years as well. He left in 1903 to become the rector of Christ Church Cathedral in Montreal.

1902
The inaugural meeting of the TCS Ladies Guild was held at the home of Mrs. Edmund Osler in Toronto, at the suggestion of the headmaster, Dr. Symonds. The initial purpose of the meeting was to complete the School chapel and otherwise further the interests of the School.

1903
The Reverend Oswald Rigby began his 10-year term as headmaster.

1908
TCS won its first Little Big Four Football Championship. Several members of the team went on to further glory in football. Peter Campbell and Jack Maynard captained the University of Toronto team in successive years, George Laing captained McGill and Styx Macaulay, RMC.

1913
The Reverend Graham Orchard was appointed headmaster, a position he would hold for the next two decades.

1915
A Junior School for students under age 15 was established, with an initial enrolment of 16 students. Although they had a separate classroom, dormitories and table at meals, they were housed in the main school building along with the older students.

1924
A new Junior School building with facilities for 78 students aged seven to 14 was opened. It was built as a memorial to those alumni who gave their lives during WWI. Howard Boulden was named the master in charge of the Junior School (today known as Boulden House).

1928
For a second time, the Senior School buildings were gutted by fire. This time, the fire began in the covered rink and spread quickly to the gym and the main school buildings. Without adequate fire fighting equipment, the blaze burned itself out through the night leaving an empty shell of brick. There were no injuries and the Senior School moved to Woodstock College, in Woodstock, Ontario.

1930
On May 1st, the new buildings in Port Hope were opened by the Governor General Lord Willingdon.

1933
Philip Ketchum was appointed headmaster. Until Dr. Ketchum's appointment, the headmasters (by constitution of the School) were required to be clergy of the Church of England. But, at a special meeting of the Governing Body in 1933, this condition was deleted.

The world economic crisis worsened and the School was faced with declining enrolment and a huge debt incurred by the construction of new buildings.

1936
The Cadet Corps became affiliated with 110 Squadron RCAF reserve, making it the first school corps to be attached to an Air Force unit.

1937
A debt of a quarter of a million dollars was paid off through the generosity of Mr. Britton Osler and 70 alumni and friends.

1941
Mr. Charles Tottenham (later the Marquis of Ely) was appointed head of the Junior School, a post he held for the next 40 years.

1950
The rink, given in memory of G.C. Peter Campbell '09 by his great friend C. George McCullagh, was opened, making TCS the first Canadian independent school to have its own artificial ice rink.

1951
The Memorial Chapel, built to honour the 185 alumni killed in the Boer War, WWI and WWII, was opened. The consecration of the chapel was presided over by the Reverends L.W.B. Broughall and R.J. Renison, both alumni. Also attending were the Governor General Viscount Alexander and his wife, and the Right Honourable Vincent Massey.

1956
The TCS Fund was instituted to provide funds for scholarships, bursaries and capital improvements to the School.

1957
Bickle House, named after Thomas H. Bickle '32, who drowned in a boating accident, was built. Through the largesse of Thomas's father, E.W. Bickle, and later the Bickle Foundation, the School was able to construct a badly needed third residence.

1962
Angus Scott became the eighth headmaster. He had been on the staff since 1952 and was assistant headmaster since 1959. He would remain headmaster until 1983.

1968
Major additions to the physical plant, including the new gym, science wing, library, administrative offices and additions to Bickle and Boulden Houses, were completed. That same year the new residence, Ketchum House, named for P.A.C. Ketchum, who had died two years after his retirement in 1962, was officially opened.

1972
The Cadet Corps was disbanded.

1981
Due to the declining enrolment of younger students, the Junior School was closed and Charles Tottenham retired.

The newest residence, Burns House, named after one of the School's greatest supporters, C.F.W. Burns '25, was officially opened by Lieutenant Governor John B. Aird.

1983
Rodger Wright, a UCC alumnus, was appointed headmaster.

1985
The growing "day student" population received its own house, named after renowned TCS master Birnie Hodgetts.

1991
The School became co-educational, enrolling its first female students.

1999
The Junior School was re-opened in Boulden House under the direction of Barbara Winsor Piccini.

2002
LeVan Hall, a hub of arts facilities including music rooms, a theatre, performance studios and the R. Samuel McLaughlin Art Gallery, was opened.

2004
Stuart Grainger was appointed the 11th headmaster of TCS.

2005
The School's archives were named in honour of John D. Burns, former master and School archivist.

2006
Application is made to create the TCS Foundation, responsible for the School's endowment fund.

2007
TCS announces a new mission statement and vision as part of the School’s first formal strategic plan.

2009
The School launches the first Week Without Walls program that has all Senior School students and faculty out of the classroom in December for a week of community service initiatives.

2010
Opening of the Arnold Massey '55 Tennis Centre and the renovated Dick and Jane LeVan Theatre.

2011
The new visual arts wing was opened.

2013
Public launch of the largest fundraising campaign in the School's history with a goal to raise $33.5 million.

2015
Trinity College School celebrates its 150th anniversary on May 1st.

Official opening in November of the Learning Commons, including a new common area and renovated Senior School library, guidance, academic support and administration spaces. In May 2016, the new facility is officially dedicated and blessed as Cirne Hall in recognition of lead donor Lewis Cirne '89.

2017
Construction of the Arnold Massey '55 Athletics Centre, including three gymnasiums, two additional squash courts, training centre, athletic therapy clinic, classroom and office space.