Yes in 1864 the US Dollar reached its lowest level compared to the Canadian Dollar ($2.78 US Greenback Dollars to one Canadian Dollar in July 1864), but within a few years that had been corrected (and that return to the Gold Standard, was the chief reason for the "Long Depression" of the 1870s, the US Dollar only returned to par with the Canadian Dollar in 1879).
During most of US and Canadian history, dollars were usable on both sides of the Border (Which is one of the Reasons the Canadians ended up adopting the Dollar officially in the 1850s). In many ways the adoption of the Dollar in Canada was the acceptance that if the US ever wanted Canada, Canada would become part of the US (The Confederation of 1867 was done more to reduce any US desire to take Canada then any other single factor).
Anyway, US and Canadian Dollars were almost exchanged one to one till about 1905 when it became illegal to use US Dollars in Canada, even afterward US and Canadian Dollars stayed roughly one to one till the 1960s, when a greater divergence was permitted (Canada Dollars suffered during WWI, but so did the currency of the rest of the World compared to the US Dollar, Canadian dollars dropping to .84 Cents US in 1920, returning to almost par in the 1920s, but falling to .80 cents in 1930 as the great depression kicked in. Canada made the same mistake the US did in 1865, tried to return to the Gold Standard when it would have been better to abandon the gold Standard permanently, as everyone has done since the Great Depression).
More on Canadian Dollars:
More on the Adoption of the Canadian Dollar and the affects of the US Civil War:
http://www.bankofcanada.ca/wp-content/uploads/2010/07/1854-1914.pdfThe complete paper that the above article is just one chapter of:
http://www.bankofcanada.ca/publications-research/books-and-monographs/history-canadian-dollar/http://en.wikipedia.org/wiki/Canadian_dollarYes, the biggest Factor in Canada's use of the Canadian Dollar has been that it is tied in economically with the US. Canada can do things like adopt a dollar coin and drop the Dollar bill (Advocated in the US for decades, but has never been done in the US, but was done decades ago in Canada), plastic money instead of linen paper and other such minor variations, but as to permitting the Canadian Dollar to vary to much from the US Dollar, unacceptable and intolerable. The two Nation-State of Canada and the US are actually in fact one large economic country and has been since before the US Revolution. As such both Nation-States must work in conjunction with the other, and given that the US is that much larger then Canada economically, the US calls the shots and Canada has the right to object, but Canada will NOT oppose anything the US economically does. Both the US and Canada are two Nation-states of the same Economic Country.