April 15 – Ten thousand demonstrate at Queen's Park in support of the striking Toronto printers. The police, prompted by the Masters Printers' Association and its leader, George Brown of the Globe, arrest the entire 24-man strike committee.
April 18 – John A. Macdonald introduces a bill to legalize trade unions.
April 25 – The first issue of the weekly Ontario Workman is published by the Toronto Trades Assembly. It is Canada's first labour newspaper.
May 15 – In the first nationwide labour protest, marchers across the land press for the nine-hour workday.
June 14 – The Trade Unions Act is passed in parliament, legalizing labour unions. The Criminal Law Amendment Act is also passed, making picketing illegal.
Elijah McCoy, born in Colchester, Ontario, invents the first of his many devices to oil engines used on trains and in factories.
The new Patent Act encourages import or licensing of technology and foreign patents by allowing legal use of patents in Canada if not registered in Canada within two years.
^"Report of the Minister of Agriculture [for] 1872," pg. 8 (frame p. 26-8'), Sessional Papers; Volume 6; First Session of the Second Parliament; Session 1873. Accessed 19 February 2023
^Letter "Copy - No. 79" Return to an Address of the House of Commons, Dated 31st March, 1873, Asking for Copies of All Communications from Indians or Others in Manitoba, with the Government on the Subject of the Dissatisfaction Prevailing among the Chiefs, Headmen, and Indians Treated With in Manitoba, and Adjacent Territory in the Year 1871 (1873), pgs. 3-4. Accessed 15 September 2018
^Sandford Fleming, Progress Report on the Canadian Pacific Railway Exploratory Survey (1872), pgs. 15-16. Accessed 15 September 2018
^George Monro Grant, Ocean to Ocean: Sandford Fleming's Expedition through Canada in 1872 (1873), pgs. 40-1. Accessed 15 September 2018