Mike Sweeney,
Shackelford's reference is the first one I can think of offhand.
I agree with your assessment of the supposed "school" although I am not even sure fraternity quite applies. I'm not sure Tillinghast and Flynn were "brothers" when it came to matters of golf course design, or anything else for that matter.
I'd missed that thread you posted, and find it pretty funny reading. Pinehurst was the main influence on Philadelphia architecture? That is rich. I also like how TEPaul and Cirba tried to squeak Fownes into the same supposed "school" grouping. Let's see . . . Boston is about the same distance from Philadelphia as is Pittsburg, so perhaps they ought to throw in Leeds as well, for good measure. And it is great how Tom Paul is pretending to have coined some important phrase because he tried to stick the world "original" on the front of Shackelford's "Philadelphia School."
The wishy washy nature of their efforts says something about the legitimacy of this supposed school.
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Dan, Those are two examples of actual movements in art spearheaded by a few artists and their followers. The "Philadelphia School" of golf design wasn't anything like those, was it? In both cases there was a strong stylistic approach associated with the "school." It wasn't just a mere geographic or tenuous social connection.
What was the central driving style or tenant that runs through the work of all in the supposed Philadelphia School? Who was the founder, mentor, leader, teacher? What was the thread that ran through all of what they produced? Pine Valley was heavily influenced by Colt, so is he the founder of the School? Merion was designed according to the ideas of CB Macdonald, so was he the founder of the school? AWT worked early on with Peter Lees, among others. Is he in the school, too? Thomas was heavily influenced by Bell in California and the vast majority of his work was in California, so how does that work? Can we throw Bell in because he grew up over 300 miles away in Pittsburg? Or how about Donald Ross or Walter Travis? Cirba seems to think that the work they did at Pinehurst provided the basis for the Philadelphia School, and Travis did have involvement at Pine Valley, and even drew up plans. So is Travis in the school? Is he the main figure?
In short, it doesn't seem like the supposed "Philadelphia School" was anything like the schools or movements you mention. Or was it?