He was 11 years old when he and his brother Jack found it inside a livery stable. The boys were helping their father dismantle four buildings along the Shenango in preparation for the viaduct's construction.
Now, 76 years later, explosives experts are plotting out a plan to find that dynamite and remove it from the cellar where it was buried and covered with dirt. PennDOT says it is spending up to $100,000 to search for and safely snuff the cases of dynamite and nitroglycerine caps.
Until now, Anderson, 87, has stayed out of the limelight that's now shining on West Middlesex's unusual predicament. With a little pushing from his children, he agreed to an interview with The Herald.
From his Hermitage home, the Westinghouse Electric retiree remembers in finite detail the hot, dry summer he and his brother helped their dad tear down two stores, a livery and a stable that stood near where O'Neill Coffee Co. now stands on Main Street.
"Dad went fishing and Jack and I found these cases," Anderson said. "I thought I found firecrackers."
He grabbed one of the crates and "slid down the hill" to where his dad was fishing. His dad froze as soon as he saw the nitroglycerine caps and told Anderson sternly, "Don't move."
"I could see my Dad was scared. He didn't show emotion (often,)" Anderson said.
The boys showed their dad the other boxes, and Anderson remembers his dad opening one of the cartons and finding the sticks of dynamite packed and padded in sawdust. His dad wiped beads of moisture off the sticks. He threw one to the ground and it ignited a big spark.
Explosives experts have told PennDOT the dynamite actually is more dangerous today than it was decades ago.
Anderson, who grew up in the village of Greenfield, about five miles east of West Middlesex, said his dad told West Middlesex officials what the boys had found. The borough council decided the Andersons couldn't move the cartons through town.
The only option at the time, he said, was to bury the boxes.
They found an empty coal cellar. It had a rock ceiling and floor and a heavy door. Officials agreed it was the best place to put the dynamite. They put a heavy lock on the door and blockaded it more with a set of four cast iron seats from a theater.
Workers leveled the site and covered the cellar with dirt.
"There was no sign of it two days later," Anderson said.
Last summer, when he learned of PennDOT's plan to replace the viaduct, Anderson immediately was worried that the construction work would aggravate the dynamite. He had planned to attend a public hearing, but was unable to go. Instead, he sent PennDOT a letter outlining his memories and concerns.
"They said it was a good thing I didn't go to the meeting," Anderson said.
Since then, he's made three trips with PennDOT engineers to the spot where he believes the dynamite is buried. They've questioned him over and over again, especially since they didn't think the demolition work for the viaduct would have been happening as early as 1936. PennDOT records indicate the viaduct was built in 1941. Anderson graduated from high school two years later.
But Anderson said he knows his dates are right. They tore down the buildings in 1936, and a year later used some of the lumber to add on to the family's home. His father married Anderson's stepmother in 1937, and they needed more space because there were more children on the way.
Anderson, who easily rattled off the measurements of the rooms inside his childhood home and spoke at length about his fight to join the military and serve in World War II, said he believes it's actually PennDOT that has its dates wrong. He thinks the bridge, built by the WPA (Works Progress Administration), was dedicated in 1941, but that it was opened to traffic far ahead of that date.
That detail aside, Anderson said simply he's glad to be of help. Jim Carroll, a district press officer for PennDOT, said the agency is grateful Anderson came forward.
His children are proud of him and urged their father to step forward as the mystery letter writer. They suspect anyone else who may have helped clear buildings at the site or known about the dynamite has died.
Anderson's son, Ed Anderson Jr., said, "If he wouldn't have lived they never would have known about it."
For that, the elder Anderson credits his late wife Margot. The two met in Germany during WWII and were married 62 years when she died three years ago.
Anderson Jr. said he considers his Dad a hero, a man who spoke up and likely prevented harm to others. "That could have been a serious, serious thing."
Information from: The Herald, http://www.sharon-herald.com