Under the Northwest Territories Act the Assembly is officially defined under federal law as Legislative Council. However under Northwest Territories territorial law, it is defined as Legislative Assembly. Under different periods of its history it has alternated names.
The very first election to the Assembly would take place on March 23, 1881 as Lawrence Clarke was elected to represent the electoral district of Lorne. In 1883 the Assembly moved south to Regina based on amendments to the route of the railway. The first territory-wide election took place on September 15, 1885 known as the 1885 Northwest Territories election.
Three years later the first general election took place. All the voting members of the Assembly were elected for the first time, and an elected speaker took office. The Lieutenant Governor still had executive authority however and appointed and ran the cabinet. After the second general election in 1891 the first fully elected Assembly without any appointed members. The Assembly achieved Responsible Government for the first time in October 1897 as the Lieutenant Governor appointed Frederick Haultain as the first Premier to form a government. Robert Brett became the first Leader of the official opposition and party lines were roughly drawn based on Conservatives and Liberals.
The Haultain government lobbied for Government of Canada for provincial powers for the Northwest Territories. In response on September 1, 1905 the provinces of Alberta and Saskatchewan were created by Prime Minister Wilfrid Laurier out of the southern populated portion of the territories.
Frederick White was appointed as the first Commissioner and did not recall the council to sit during his time in office. The first session of the 2nd Council of the Northwest Territories took place in 1921. The council members were bureaucrats appointed from the Interior Ministry and were not resident citizens of the territory. In 1947 The first Northwest Territories resident since 1905 was appointed to the council. John G. McNiven was appointed to represent Yellowknife. McNiven was also the first member appointed to the council from north of the 60th parallel.
In 1951 the council held its first general election in 49 years. The fifth general election elected three members from the District of Mackenzie. The old council was completely dissolved and five members were appointed along with the three elected representatives.
The council gained more powers back from the federal government as the population in the territory grew. In 1967 the Carrothers Commission moved the territorial capital from Ottawa to Yellowknife and for the first time elected members represented all parts of the territories. In 1975 the Legislative Assembly became fully elected, and the first elected speaker David Searle, since 1905 presided over the Assembly.
The modern Consensus Government model is inherently non-partisan and serves effectively as a constant minority government. The Legislature uses this model up to the current day.
The building that has housed the Northwest Territories Legislative Assembly has changed many times since it was founded. The first building was the original Manitoba Legislature in Fort Garry. After the council moved to Fort Livingstone it was housed in the Swan River Barracks used by the North-West Mounted Police.
The first building built for the needs of the Assembly was NWT Government House in Battleford. That building also served as a residence for the Lieutenant Governor. In 1883 the Assembly moved to Regina. The Territorial Administration building was built to accommodate the growing Assembly and used until 1905.
After the creation of Alberta and Saskatchewan, the capital was moved to Ottawa and the council sessions took place in an office building on Sparks Street. When the council sessions returned to the territories, they were held in any infrastructure suitable as they traveled from community to community.
After the capital was moved to Yellowknife in 1967 a temporary site for the Legislative Assembly was used until the new Legislature building was finished in 1993.
Despite attempts by political parties to run candidates for the legislature, the legislature is nonpartisan and has been since 1905.