Where was Once Upon a Time in the West Filmed?

The majority of the film Once Upon a Time in the West was filmed on location in the Monument Valley area in the United States. Sergio Leone, the director, wanted to create an authentic Western landscape, so he insisted on shooting in Monument Valley, which had previously been used as a backdrop for many classic Western films. Leone made use of the dramatic rock formations and vast expanses of the valley to create the stunning visuals for which Once Upon a Time in the West is known.