Sub-sub-series consists of files containing correspondence, notes, memoranda, etc. pertaining to a wide variety of technical issues governing the compilation of individual map sheets. For example, many of the records found in each file document the naming of geographical features. Also included are various orders-in-council and acts of Parliament which define the boundaries to certain federal lands, such as Indian reserves and national parks. These features were eventually added to subsequent editions of the maps. The files also contain a wide range of correspondence from various people pointing to the errors they found on individual map sheets.
Although some of the records contained in these files date as late as 1965, most were created in the period between the First World War and the late 1920s that is, the period when the maps were most popular, before they were supplanted by mapping under NTS. (RG88, Vols.503-510)
With the expansion of eastern Canada to the prairie frontier following confederation, the Dominion government began a cadastral survey to subdivide the new lands into townships measuring six square miles each and subdivided into 36 sections. In an effort to provide an orderly system of settlement, the Dominion Lands Act required that an approved surveyor's plan of the township had to be registered at the local land titles office before the township could be opened to settlement. Administrators of the Dominion Lands Survey and the homesteaders themselves soon created a demand for maps which summarized known geographical information on the various townships as well as the progress of settlement.
After several preliminary attempts, the Three-Mile Sectional Map was introduced in 1891. Scaled at 1:190,080 (or one inch to three miles), the Three-Mile Sectional Map was the first extensive series to be developed independently by the Canadian government without outside assistance from a foreign mapping agency. The map was closely tied into the Dominion Lands Survey system. Each sheet was designed to accommodate 8 ranges (north/south) by a maximum of 15 townships (east/west) or 48 miles by 90 miles. The projection was a simple conic with the control meridian placed at either the eastern or western end of the sheet.
Although the Three-Mile Sectional Map originally focussed on the farm and ranch lands of the west, the grid was eventually extended as far north as Dawson City, as far west as Kamloops, and as far east as Lake of the Woods. In total 134 sheets were issued in the series, covering an area about 1,400,000 square kilometres. Most of the sheets were updated regularly, with those from more populated areas issued in more than 10 editions.
With the decision to proceed with the National Topographical System (NTS) in the 1920s, the Three-Mile Sectional Map was not immediately abandoned but the extent of its coverage was curtailed. The existing sheets were still updated regularly with the last revision issued in 1955. The last sheet to be withdrawn from sale was in 1967 when it was replaced by a sheet in the NTS 1:250,000 series.
