In April 1975, the American Freedom Train set out on a tour across the United States to celebrate 200 years of American independence.

On-board were more than 500 priceless artefacts, documenting important moments in America's history - including an original copy of the Constitution, Thomas Edison's first working light bulb and a NASA lunar rover.

Over the next 21 months, seven million people visited the travelling museum as it made its epic journey around 48 states.

Jacqueline Paine speaks to former train security guard Lou Nelson, about taking America's history to the people, as the country prepares to celebrate its 250th anniversary.

Eye-witness accounts brought to life by archive. Witness History is for those fascinated by the past. We take you to the events that have shaped our world through the eyes of the people who were there.

For nine minutes every day, we take you back in time and all over the world, to examine wars, coups, scientific discoveries, cultural moments and much more.

Recent episodes explore everything from the death of Adolf Hitler, the first spacewalk and the making of the movie Jaws, to celebrity tortoise Lonesome George, the Kobe earthquake and the invention of superglue.

We look at the lives of some of the most famous leaders, artists, scientists and personalities in history, including: Eva Peron – Argentina’s Evita; President Ronald Reagan and his famous ‘tear down this wall’ speech; Thomas Keneally on why he wrote Schindler’s List; and Jacques Derrida, France’s ‘rock star’ philosopher.

You can learn all about fascinating and surprising stories, such as the civil rights swimming protest; the disastrous D-Day rehearsal; and the death of one of the world’s oldest languages.

(Photo: Local people in Archbold, Ohio queue to see the American Freedom Train, June 1975. Credit: AP)