This comprehensive 15-part retrospective, anchored by Peter Jennings, takes an era-by-era look at America's evolution during the turbulent 20th century.This comprehensive 15-part retrospective, anchored by Peter Jennings, takes an era-by-era look at America's evolution during the turbulent 20th century.This comprehensive 15-part retrospective, anchored by Peter Jennings, takes an era-by-era look at America's evolution during the turbulent 20th century.