In its purest form, skateboarding is a simple act of gravity. Point your board downhill, step on and let Newtonian physics dictate what happens next. Pretty basic stuff, really. Unless, of course, you were standing on your skateboard during the mid-1970s at the top of Southern California's infamous Signal Hill. From there, a downhill speed run wasn't so much an easy surrender to a grand force of nature as it was a potentially deadly leap of faith.

That dangerously steep drop -- with all its broken bones, bloody bruises and high-performance breakthroughs -- is the subject of "The Signal Hill Speed Run," a feature-length documentary now making the film festival rounds.

The film gets going in 1975, when Jim O'Mahoney -- described as the P.T. Barnum of skate contest promoters -- organized the first Signal Hill event after getting a call from producers at "David Frost Presents the Guinness Book of World Records," an ABC "Wide World" special.

Having grown up surfing, skating and hang gliding in and around his native Long Beach, Calif., O'Mahoney -- who bombed Signal Hill on his bike as a boy -- was hardwired for adrenaline, and he had no intention of organizing something cute and surfy.

Let's take Signal Hill from the top, he told ABC. Winner takes all.

To read the rest, check it out here on XGames.com.