Canada's five oldest provinces – New Brunswick, Nova Scotia, Ontario, Quebec and Prince Edward Island – are divided into counties. In those older provinces that have a two-tier system of municipal government, the counties constitute the upper tier and local municipalities form the lower tier. In addition to counties, Ontario is also subdivided into territorial districts, district municipalities, metropolitan municipalities, and regional municipalities which are also part of the upper tier. British Columbia is divided into regional districts that form the upper tier. They are subdivided into local municipalities that are partly autonomous, and unincorporated electoral areas that are governed directly by the regional districts. The rest of Canada has only one level of municipal government. Manitoba, Newfoundland and Labrador, Northwest Territories, Nunavut, Saskatchewan, and Yukon use their municipalities as regional and local subdivisions without any real differentiation between the two. In Alberta, a "county" used to be a type of designation in a single-tier municipal system; but this was changed to "municipal district" under the Municipal Government Act, when the County Act was repealed in the mid-1990s, at which time they were also permitted to retain the usage of county in their official names.