The big top at the Ringling Brothers and Barnum & Bailey Circus soon became engulfed, sending the matinee crowd of 6,000 - mostly women and children - scrambling for their lives.
The tent was waterproofed with 1,800 pounds paraffin thinned with 6,000 gallons of gasoline and burned quickly to the ground, giving those inside little time to escape.
In the panic to flee, people climbed over animal chutes and toward exits. Some fell and were trampled. Most victims were found piled up near an exit blocked by animal cages.
The blaze killed 168 people and injured 700 on July 6, 1944. Spada, who was 8 at the time, escaped with her parents and two sisters, but lost two relatives.
``My mom and dad went to the funeral of my aunt and cousin, but after that we never talked about it. I don't know why. It was just too painful, or that generation just never talked about things like that,'' she said.
On Tuesday, Hartford plans to break ground on a memorial to the victims, which will be located where the center ring once stood. It will have the names of those who died etched in blue stone and include pedestrian pathways lined with plaques and bricks carrying messages of victims' families, survivors and other contributors.
It is hoped the memorial will be completed by fall.
The youngest survivors of the fire are now in their 60s, but most were too grief-stricken to think about building a memorial before, said Hartford Fire Chief Charles A. Teale, a co-chairman of the Hartford Circus Fire Memorial Foundation, which has raised more than $100,000.
``It was during the aftermath of depression and during World War II. People were already overwhelmed with the experiences of life. They went to the circus for entertainment, and came away losing 100 children and 68 adults,'' Teale said.
The cause of the fire was initially blamed on a smoldering cigarette, but police later concluded it had been set. State police reopened the case in 1991 to investigate whether arson was involved, but eventually reclassified the cause as undetermined.
Eunice Groark, the state's former lieutenant governor, was 6 when she attended the circus with her mother and her mother's nurse. She said she continues to be haunted by the screams she heard and the sight of the circus tent, consumed by fire, crashing to the ground and trapping victims underneath.
``I am still terrified. When I go to the movies or am in a big crowd, I need to find the exit,'' she said.