The story begins in a drill hall. On November 5, 1880, the Cartier Square Military Museum was established to preserve records and materials of the Canadian Militia and its colonial predecessors. Within six years, the collection had outgrown its space. By 1896, the museum was closed entirely - not because it failed, but because the military needed the room for a shipment of Lee-Enfield rifles. The collection was stored in an old warehouse below Parliament Hill. The Department of Militia and Defence leased a building in Ottawa in 1901 but never bothered reopening the museum, letting the lease lapse in 1905. Only when Dominion Archivist Arthur Doughty requested the artifacts for display did the military hand over 105 items between 1910 and 1919, washing their hands of the responsibility. The Canadian War Museum was not formally established until January 1942 - midway through the very kind of global conflict its collections were meant to commemorate.

For decades, the museum operated in inadequate spaces. After moving into the former Public Archives building in 1967, conditions deteriorated so badly that a 1991 government task force called the museum's state "embarrassing" and a "national disgrace." Some areas were environmentally hazardous for displaying artifacts. Funds for expansion were limited by federal austerity measures in the mid-1990s. A supporters' group, the Friends of the Canadian War Museum, formed in 1995 to assist fundraising. A proposed Holocaust exhibition in 1996-1997 ignited fierce debate - Canadian veterans felt marginalized, and historians questioned whether a war museum was the appropriate venue. Senate hearings followed. Adrienne Clarkson, then chair of the Canadian Museum of Civilization Corporation, ultimately shelved the Holocaust exhibit but pushed forward with plans for a new building. Barney Danson, appointed to the board in 1998, helped secure property near CFB Rockcliffe - though Prime Minister Jean Chretien later intervened to move the site to LeBreton Flats.

The building that Moriyama and Teshima Architects designed with Griffiths Rankin Cook Architects opened in 2005 on formerly industrial land at LeBreton Flats, southwest of Parliament Hill. The National Capital Commission had to decontaminate the property before construction could begin. The museum draws water from the adjacent Ottawa River for mechanical cooling and irrigation. Inside, the Canadian Experience Galleries unfold chronologically across four halls: from the Beaver Wars and Anglo-French conflicts through the War of 1812 and North-West Rebellion; through the Boer War and First World War (with a gallery styled to evoke Queen Victoria's diamond jubilee of 1897); through the Second World War (featuring Hitler's Mercedes-Benz 770K, acquired in 1970 under the mistaken belief it had belonged to Hermann Goring); to the Cold War and present-day conflicts involving the Canadian Armed Forces.

Memorial Hall sits in the museum's lobby, its smooth concrete walls arranged in a grid that echoes the headstones of First World War cemeteries. At the building's highest point, Regeneration Hall serves as what the museum calls a "physical representation of hope for a better tomorrow" - its angled walls framing a view of the Peace Tower on Parliament Hill through an eastern glass facade. The Royal Canadian Legion Hall of Honour, an oval-shaped gallery, traces how Canadians have commemorated military service throughout history, with floor-to-ceiling display cases holding medals, photographs, letters, and scrapbooks. The museum receives roughly 700 donation offers per year but accepts only 100 to 150. Canadian service medals and medals of valour, however, are accepted unconditionally as an "act of honouring." By 2019, the museum held 39 of the 99 original Victoria Crosses awarded to Canadians.

The Beaverbrook Collection of War Art - named for Max Aitken, 1st Baron Beaverbrook, who established the Canadian War Records during the First World War - contains over 13,000 works of military art, including more than 340 pieces by Alex Colville. The collection arrived in stages: the National Gallery of Canada transferred management of the Canadian War Memorial Fund and over 5,000 works in 1971. Of those 13,000 works, only 64 depicted a dead body as of 2017. The Military History Research Centre maintains an oral history archive of nearly 400 interviews with veterans of conflicts from the Second World War to Afghanistan. The museum's photographic archives hold more than 17,000 individual photographs and 250 photo albums, most donated by participants in the conflicts they document. It is a place that takes the full weight of war seriously - in concrete, in art, and in the voices of those who served.