Twenty years ago, at 4 p.m. on July 6, a wave of flame swept along a ridge on Colorado's Storm King Mountain, killed 14 firefighters, and became a benchmark for wildland firefighting with repercussions that continue to this day.

On Sunday, firefighters from across the nation will gather at the site of what became known as the 1994 South Canyon Fire, about seven miles west of the resort town of Glenwood Springs in central Colorado, to mark the anniversary and take stock of its legacy.

For many of the specially trained crews that battle mountain wildfires in the American West, it was a blaze that made it more acceptable for firefighters to speak up or even decline assignments they consider too dangerous—once