The PBS Nova film, in three-episodes of one hour each, was hosted by Kirk Johnson (Director of the Smithsonian National Museum of Natural History); Peter Oxley directed the first episode while Gwyn Williams directed the second and third. The series describes the very beginnings and later developments of the North American continent: from the origin of planet Earth 4.54 billion years ago; to the various movements of tectonic plates and their effect on the sculpturing of the continent's land and mountains, including the Rocky Mountains, Yellowstone and the Grand Canyon; to the emergence of life on the continent and its later evolution; and, finally, to the more recent settlement of the land by humans. According to Johnson, "Most people will not have considered a time when there was no North America ... What was there before North America? How did it form? When did it start? How did it come together?"