It was the product of a merger between the Montreal Citizens' Movement (RCM) and a group of suburban politicians who backed Gérald Tremblay for mayor.

The new label consisted of five vertical stripes (blue, green, brown, yellow and pink), each bearing one of the letters of the word UNION.

[3] Following his resignation, Union Montreal councillors Frantz Benjamin, Michael Applebaum, Lionel Perez, Susan Clarke, Marvin Rotrand, Christian Dubois, Daniel Bélanger, Ginette Marotte, Alain Tassé and Frank Venneri all left the party to sit as independents.

[5] However, Deschamps was defeated 31 to 29 by Applebaum,[5] who pledged to run a non-partisan coalition council in which members of all parties, as well as the bloc of independents, would share seats on the Montreal Executive Committee.

In the runup to the 2013 municipal election campaign, several of its former members rallied around the candidacy of Denis Coderre,[9] who also attracted support from former Vision Montréal councillors and others.

Union Montreal's initial plan to apply for dissolution was withdrawn by September 2013, as it decided to stay in existence until the resolution of the Charbonneau commission.