The world's greatest tragedies always have given way to stories of hope, heartache, despair and determination to overcome. The London School explosion that happened 70 years ago today is no different.

Walter Cronkite, one of the 20th Century's most well-known reporters, called March 18, 1937, the "day a generation died." It is an apt description of the loss of nearly three-fifths of that school's students and teachers.

Click the image above for an audio slideshow in the survivors own words. Click the image above to see a video on London history. Click the image above for more photos. MORE NEW LONDON STORIES: Cenotaph honors those killed in school explosion  London Museum houses items from tragic day  Cemetery home to 129 killed in blast  Through their eyes: Four survivors discuss how the New London explosion changed them forever  During oil boom, before explosion, the school was the PRIDE of New London  Reporters converge on New London  Odor now added to natural gas  Community gathers to honor those who died in school explosion and those who lived  Faces, forever changed: School blast survivors still unable to talk about those they lost  Remembrances roll as London School graduates gather  Silence was normal for many survivors  A shared pain: London School graduates gather to mark blast's 70th anniversary  Explosion survivor's faith still strong after tragedy

"We weren't allowed to talk about it. We were not allowed to talk about it at all," said Joan Barton, 77, who was a second-grader when leaking gas ignited 13 minutes before school was to close for a three-day weekend. "We probably lost a lot of memories. I just remember my mother screaming."

The screams perhaps seemed endless that night as parents, reporters, oil field workers and anyone who could help descended on the town of New London.

The explosion is considered the third deadliest tragedy in Texas history, ranking behind the Galveston hurricane of 1900 and the Texas City disaster. While no exact count may ever be determined, 298 students, teachers and others are believed to have died when manual training instructor Lemmie R. Butler turned on a sanding machine. He had no idea that the area was filled with a mixture of gas and air.

The mixture ignited, carrying the flame into a nearly closed space beneath the building, which then was lifted into the air and smashed to the ground, according to www.nlse.org, a Web site about that day and the memories that followed.

Marvin Dees was working with a crew at an oil lease about five miles south of London when he heard the explosion. A few minutes later, the lease operator came and told them what had happened. The crew piled in a truck and rushed to the site.

"By that time, there were men coming from all directions," said Dees, 91. "We just started moving debris, removing bodies, body parts, whatever, and those that were still alive.

"It was gruesome. I was only 21 years old, but I think I aged 10 years that night, because I saw things that I had never experienced."

Dees worked in the recovery from 4 that afternoon until 10 the next morning.

He now makes the half-hour drive from his Tyler home to the London Museum and Tea Room once a week for lunch and recollection.

"I can remember everything so clearly," he said. "I could just remember exactly where I was, everything that was going on. It was a disaster, because the oil field was booming at that time, and a lot of people were moving all over the oil field."

Indeed, before 3:05 p.m. on March 18, 1937, the London School in Rusk County was a tangible example of the East Texas oil boom of the 1930s. Less than seven years before, wildcatter Marion "Dad" Joiner and his Daisy Bradford No. 3 well inaugurated what was then the largest oil field in North America. In 1931, existing towns swelled 10 times their size overnight, and new towns were formed. Wealth was abundant, and nowhere was that more evident than in London, which proclaimed it had the world's richest school district.

The London School, with a price tag of $1 million, was built in 1932 as a modern, E-shaped building. Officials said they spared no expense, boasting East Texas' only illuminated football stadium, a manual training shop and custom-tailored band uniforms.

To cut costs, however, gas steam was substituted for a central steam-heating system that required gas lines to be run under the school.

That proved fatal because no one could smell the gas as it leaked.

"I believe there's something good that comes out of everything that's bad," said Dees, a retired mechanical engineer from Texaco, which was called The Texas Company in 1937.

"The only good thing was that they started putting an odorant in gas ... and who knows. That could have saved hundreds of lives years after the explosion."

The memory of her mother's screams and the inspiring words from an unlikely source brought Barton to tears 70 years later while eating pot roast and potatoes at the London Museum, where she has volunteered almost daily since it opened in 1994.

Her mother, who had four children, was frantic over Barton's older sister, Jane, a fifth-grader who was in the main school building at the time of the blast.

It was the mother of Jane's classmate and boyfriend who comforted her, Barton said.

"She told my mother, 'Now, you know, God takes care of everything,' " Barton remembered, "and their only son was killed."

Jane Barton was an overall-wearing tomboy who survived the explosion. The other mother, who Barton did not name, eventually had another child and named her after their deceased son's girlfriend.

"You would think, after 70 years, I'd learned not to cry," Barton said.

"It was just too sad. Of course, now, they want you to talk about it because it helps you and everything. Maybe that's why I still cry."

Barton still lives in New London. Seventy years ago today, her future husband, Gerald Barton, now deceased, was walking home from school when the blast that killed his brother occurred.

The Rusk County town earlier known as London was renamed New London when a post office came to the community in the mid-1930s and postal officials said there already was another town named London in the Texas Hill Country. At the time of the 1937 explosion, the school was still known by the older name of London.

Today, a monument and the museum are among the few permanent displays commemorating March 18, 1937.

The tiny town of about 1,000 people is filled each day with the laughter and chatter of schoolchildren enjoying recess at the West Rusk County Consolidated Independent School District, whose high school and junior high building were constructed at the blast site.

There is little semblance of a place that holds one of America's darkest memories, where nationally known journalists such as Cronkite, Sarah McClendon and Felix McKnight got their first big stories, where tough-as-nails roughnecks cried as they carried children's body parts from rubble, and where a town's children either died — or survived and carried grief or guilt through the decades.