What makes a western a western?

Film theorist Robert Stam notes "While some genres are based on story content (the war film), other are borrowed from literature (comedy, melodrama) or from other media (the musical). Some are performer-based (the Astaire-Rogers films) or budget-based (blockbusters), while others are based on artistic status (the art film), racial identity (Black cinema), locat[ion] (the Western) or sexual orientation (Queer cinema)." So I guess it's the location that makes it a western. What about time? Can we still produce western movies now using the natural setting without creating artificial studio? Or could it have been produced in, say, 12th century? I looked up the word "western" at Wikipedia.com, and it says "The Western is a fiction genre seen in film and other visual arts. Westerns are devoted to telling stories set primarily in the later half of the 19th century in what became the Western United States (known as the American Old West) but also in Western Canada and Mexico. Classifying different genres may not be clear cut as they may often overlap, but no one can argue against its usefulness. Denise MacQuail makes this clear "The genre may be considered as a practical device for helping any mass medium to produce consistently and efficiently and to relate its production to the expectations of its customers. Since it is also a practical device for enabling individual media users to plan their choices, it can be considered as a mechanism for ordering the relations between the two main parties to mass communication."
So, what makes "the purpose of this creature man" a western? Let's look at the time and the place. I found a first clue in Doc's Hobbes motorcar. A 1906 model. With that in mind, I assumed that the story is set in 1906 or later. A Western can be as early as 1860 and as late as 1920s. Let's look at the place. Duke, whose alias given by doc, had criminal history in Missouri. Also, Doc and his gang's first score occurs in Arkansas. The problem is, these are not in west. Then I wonder if this is a Western at all. The sawed off Winchester scattergun may make this a Western. The fact that one guy organizes a gang to commit crimes also may make this one a Western. Apart from time and place criteria, what about contents? What kind of story constitutes a Western? Only the ones in which guys like Doc and his gangs rob places and spraying bullets everywhere? Because I thought "Far and Away" was a Western.