| 1923 |
Library opened on Weston Road near Eglinton Avenue. |
| 1928 |
Public library established serving York Township School Section Number 28. |
| 1933 |
Mount Dennis Public Library Board established. Library located in rented space in the old Major Theatre; library later relocated to the Legion Hall. |
| 1945 |
Mount Dennis Public Library Board dissolved. Assets (including collection of 6,000 volumes) transferred to the newly established Township of York Public Library Board. |
| 1948 |
York Township Council approves building a main library building and two branches. |
| 1950 |
Construction started, April. |
| 1951 |
Library opened at the current location, 19 March; officially opened in May. Architect Albert Vine. |
| 1960 |
"Art Room" created in the basement for exhibitions of arts and crafts, December. |
| 1967 |
Branch becomes part of the York Public Library Board, when the Town of Weston and the Township of York are amalgamated as the Borough of York, 1 January. |
| 1969 |
Branch staff continues to service patients at Northwestern Hospital with a deposit collection. |
| 1971 |
Hours of service extended with the branch opening on Wednesdays. |
| 1981 |
Hours reduced with Monday closings. |
| 1982 |
"Plans to improve and expand the Mount Dennis Branch were activated. With the receipt of a large Wintario grant, architects were hired and it is hoped construction will begin in 1983." [Annual Report, 1982] |
| 1983 |
Closed for renovation and addition. Moffat & Duncan Architects. |
| 1984 |
Reopened September. Ground-breaking ceremony for the Mount Dennis Library Extension and Renovation. [Annual Report, 1984] |
| 1985 |
"The Mount Dennis Branch was re-opened to the public on September 3rd, following extensive renovations and an addition to the main floor of the building." Officially opened September 28, 1985. [Annual Report, 1985] |
| 1986 |
"The lower level of the recently renovated and expanded Mount Dennis Branch was opened in April and became the new location of the Children's Department." [Annual Report, 1986]. |
| 1987 |
"Work on completing the millwork, book security system, elevator, outdoor sign and parking lot was undertaken with funding from the City of York and the Ministry of Culture and Communications." [Annual Report, 1987]. |
| 2000 |
Film Department closure of former York Public Library located at Mt. Dennis Branch, 14 January. |
| 2007 |
New hours, 8 January. Hours open per week decreased on 8 January from 51.5 to 50.5. |