Tom,
You wrote, "before 1850, when golfers didn't travel from course to course, their swings evolved based on the needs of their home course and the style of the best local players. So, there was a St. Andrews swing, a Prestwick swing, and a North Berwick swing, all very different from one another."
I find that a fascinating thought but wonder how the course itself would have so great an impact on a golf swing. Might it have been more a product of the equipment and balls being used. For example, the qualities found in the Gutties as a golf ball type greatly varied depending upon the talents of the person making them, as were the clubs. Wouldn't these have a greater effect on the golf swing than the course, though I am sure that they were created because of the courses they would be used on.
An example of what I am trying to say, and probably doing so poorly, was the creation of the sand wedge as a specialized club for use in a special situation (yes, I know it was a 20th century invention, just using it as an example). Before this club, players used a variety of general clubs and adjusted there swings for how they wanted to play the shot.
So, wouldn't this have been more of the case in earlier days, with swings based more on the clubs than the course?