To commemorate the 70th anniversary of the worst fire in Boston history, a few anonymous but history-minded people left flowers this week atop a plaque in a sidewalk in Bay Village. There wasn’t a better way to observe the occasion. Installed in 1993 at the Piedmont Street site of the Cocoanut Grove nightclub, the plaque is Boston’s main memorial to a world-changing disaster and the 492 people who died in it. For pedestrians who know to stop and read it, the plaque has a certain poignancy — according to an inscription, it was crafted by the youngest survivor of the fire — but it doesn’t fully capture the depth of the tragedy or its sweeping implications in subsequent years.

When flames broke out in a lounge just after 10 p.m. on Nov. 28, 1942, the Cocoanut Grove had all the ingredients of a catastrophe. The club was overcrowded; there were too few exits, most of which were obstructed or locked; decorations were made of materials that quickly ignited as the blaze spread around the club. The tragedy offered a window not just into the inadequate fire regulations of the day but also into the politics; word had it that the club’s well-connected owner had just been allowed to open a new section of the Cocoanut Grove without the proper inspections. Over time, the fire had far-reaching effects beyond tougher codes; by many accounts, medical knowledge advanced, as doctors recognized that the toxic gases associated with structure fires could be at least as deadly as flames.