Thirty years ago today, Terry Fox began his inspiring "Marathon of Hope", with the dream of running across the country and raising what was then a staggering $1 million for cancer research.

Three decades later, more than $500 million has been raised in his name since his story of courage and determination became the stuff of Canadian legend.

When Fox began his run on April 12, 1980 by dipping his foot into the Atlantic Ocean in St. John's Harbour, he said he wanted to make a difference in the lives of other people battling cancer.

His mother, Betty, says it was the time her son spent in hospital while he battled his cancer that forged his resolve to do something more that just survive.

"He never really lost sight of the patients that he left behind on the cancer ward," Betty recalled to CTV's Canada AM Monday, from St. John's, where she's marking the anniversary.

"He really wanted to do something to find the cause of cancer. And that was really the main purpose of what he did."

Fox decided to run across Canada to raise money for what was then a relatively underfunded disease. When his mother asked why he didn't take on something a little less ambitious, like running across his home province of British Columbia, Terry responded he had to do the whole country because cancer affected everyone in Canada.

He trained for his run throughout 1979, writing to the Canadian Cancer Society in October that year to ask for their support. "The running I can do, even if I have to crawl every last mile," he wrote. "…I am not a dreamer, and I am not saying that this will initiate any kind of definitive answer or cure to cancer. But I believe in miracles. I have to."

Terry's sister Judith says it's still incredible to think about what her brother did, running the equivalent of a marathon -- 40 kilometres -- each day of his 143-day Marathon of Hope. But she says that's the kind of person her brother was.

"Terry was a very determined person right from a very young person. We were all taught as children not to give up on anything we started. Certainly, I believed and knew that Terry would not give up," she said, standing alongside her parents in St. John's.

Within days of the run's start, it didn't take long before Fox's determination and spirit grabbed the attention of media outlets everywhere. TV images of the then 21-year-old running with his artificial leg and trademark gait quickly captured the hearts of the country and the donations started rolling in. Before Fox had even left Newfoundland, he had already stepped up his goal, aiming to raise $24 million -- or one dollar for every person who was then in Canada.

As most Canadians know, Terry didn't finish the run. He had to stop near Thunder Bay, Ontario, when the cancer that had started out as osteosarcoma in his knee had metastasized to his lungs.

But over those 143 days, Fox logged in 5,280 kilometres, raising $1.7 million. A week after his run ended, CTV organized a nationwide telethon in support of Fox and the Canadian Cancer Society. The event raised $10.5 million. Donations continued throughout the winter, and by April, 1981, over $23 million had been raised in Fox's name.

Fox died two months later, in New Westminster, B.C., a month short of his 23rd birthday.

Today, it's clear that Fox's legacy lives on. His name adorns more than a dozen schools across the country, more than 30 streets, one icebreaker, and a provincial park in the B.C. Rockies. There are also a number of cancer research facilities and research grants that honour his name, as well as the Terry Fox Humanitarian Award, which recognizes young Canadians whose humanitarian work reflects the ideals that Fox embodied.

People from 40 different countries run in his name every year and the Terry Fox Foundation is constantly funding research for new cures for cancer.

Fox's father, Rolly Fox, says it's heartening to say that his son's dream turned into real progress in the fight against cancer.

"Back in 1977, when Terry was diagnosed with the bone cancer, Betty and I were told his chances of survival were, I think, 20 to 50 per cent. Today, a person getting the same bone cancer that Terry had, their survival rate is way up in the 90 per cent range," he said.

"And that's all because of research."

His sister, Judith, says it's "so hard to believe" that Terry's legacy continues to this day, all over the world, but she couldn't be more proud.

"I have just an immense feeling of pride right now for what Terry started. But also for all of us, all Canadians and the citizen of the world who have kept Terry's dream alive," she said.