Cheyenne Frontier Days is the world's largest outdoor rodeo.

But how did it get started?

There are at least two versions of the start, according to the CFD website. One involves a Colorado travel agent, who was trying to drum up some business.

The second version has "The daddy of "em all" growing out of a conversation on a train.

The more widely accepted version of the story says the western celebration was the brainchild of Frederick W Angier, a Traveling Passenger Agent with the Union Pacific Railroad.

Angier allegedly suggested, in 1897, to the editor of a Cheyenne newspaper that Cheyenne should come up with a festival similar to the Greeley, Colorado "Potato Day." That led to a conversation in the Tivoli Saloon in Cheyenne, to draw up plans for a "Frontier Day" celebration that would include pony races, bronco busting and steer roping.

That event was so successful, in 1898 the event was expanded to two days, and continued to grow from there into the 10-day western celebration we know today.

But, according to the website, there is at least one other version of the birth of CFD. In a book about Cheyenne Frontier Days, author Robert Hanesworth says another version of the story of the beginning of CFD came from a train conversation between Col. E.A. Slack and Warren Richardson, who were headed back to Cheyenne from Greeley's 'Potato Day.' The topic was whether Cheyenne could host a similar celebration.

Richardson allegedly said of the idea "Cheyenne didn't raise much of anything except hell." Haynesworth says Slack took the idea and ran with it, leading to what eventually became Cheyenne Frontier Days.