Edouard Gaston Deville, Surveyor-General, recommended the establishment of a permanent observatory in Ottawa in 1887 (Hodgson, 8). One of the purposes for such an observatory was to have a central location to “store and maintain in proper working order 'a number of fine and expensive astronomical instruments” (Hodgson, 8). In 1890, a first observatory was erected on Cliff Street in Ottawa. It held transit instruments and a 6-inch equatorial telescope, used to determine time and longitude. The situation of this observatory was considered poor and Astronomy Branch staff of the Department of the Interior lobbied for the construction of a National Observatory (Hodgson, 9-10).
Chief Dominion Architect David Ewart designed the Dominion Observatory building in Ottawa, situated on the Agriculture Department's Central Experimental Farm. The building was completed in 1905. At opening, the Observatory had a staff of 31 (Hodgson, 25). The main instrument, a 15-inch refracting telescope, was the largest installed in Canada at that time. William Frederick King, Chief Astronomer for the Department of the Interior, was the Observatory’s first Director.
In 1918, the Dominion Astrophysical Observatory in Saanich, British Columbia, was opened with a 72-inch telescope to pursue observations beyond the capabilities of the Dominion Observatory in Ottawa.
The Dominion Observatory continued to be responsible for scientific research in astrophysical and allied sciences. The discovery of “Planet X” in 1928 was one of its most significant achievements. The Observatory also addressed problems of everyday application, such as time-keeping. A 28 August 1941 Order-in-Council designated the time established at the Dominion Observatory as official time for Dominion official purposes.
During its existence, the Observatory would report to ever-changing government departments and agencies. In 1936, the Department of the Interior was dissolved and a new Department of Mines and Resources was created. The Observatory reported to its Surveys and Engineering Branch. The change in structure allowed work in seismology and terrestrial magnetism to be consolidated. In 1947, the Dominion Observatories were grouped into one of eight bureaus of the Mines, Forests, and Scientific Services Branch. The Ottawa Observatory consisted of five divisions: Positional Astronomy, Stellar Physics, Terrestrial Magnetism, Seismology and Gravity. In January 1950, after another restructuring, the Observatory began reporting to the Department of Mines and Technical Surveys.
In 1966, the Department of Energy, Mines and Resources (EMR) was created and the Dominion Observatory became part of the Mines and Geosciences Group. The 1966-67 Annual Report for EMR describes the Observatories Branch as concerned with two major disciplines - astronomy and geophysics. A new division Astronomy, Ottawa - was created, which comprised the former divisions of positional astronomy and stellar physics. There were also three divisions concerned with geophysics.
The National Research Council (NRC) gained responsibility for the time and solar observation functions of the Observatory in 1970. The site and its equipment were thereafter used primarily for public demonstration. In 1974 the telescope was transferred to the Canada Science and Technology Museum and Mary Grey, one of the last Observatory staff working on the site, joined the Museum staff as head of its Astronomy Division.