The fact that Henry George has an ardent group of disciples who have a practical program for reform of taxation has tended to obscure from the recognition of students of social theory that his is one of the great names among the world's social philosophers. It would require less than the fingers of the two hands to enumerate those who from Plato down rank with him . . .
Dewey is sticking up for him in this comment amongst other professors quoted, as in his day Henry George was fairly controversial. Back then nationalization of the land was not looked at quite so fondly, which is one of the things that George had called for: (page 295)
We must make land common property
Henry George was right when he said that while socialization of natural opportunities, the land and the materials and power that come from it, is not a panacea, it is the foundation measure. but it is difficult to put this measure through on the scale necessary as long as it stands alone. As an integral and basic part of a larger program of socialization such as this Conference stands for, its appeal will be irresistible.
As I wrote recently regarding the "Nationalist Clubs" that once existed in America, so too did Single Tax Clubs and Leagues have their effect.
While Dewey doesn't say who those ardent disciples are, he makes it fairly clear that he is himself one. I was able to find another high profile voice in his favor; Upton Sinclair. In 1924, Sinclair wrote this:
So, I no longer advocate the Single Tax. I advocate many taxes. I want to tax the rich man's stocks and bonds, also his income, and his inheritances, and his wife's jewels. In addition, I advocate a land tax, but one graduated like the income tax. If a man or a corporation owns a great deal of land, I want to tax him on the full rental value. If he owns only one little lot, I don't want to tax him at all.
So prior to 1924, Sinclair was a Georgist. This is his turning point on the matter. But we don't have to look so high for evidence of how wide spread George's ideas had become. Earlier I mentioned Single Tax Clubs, here is a menu from the Manhattan Single Tax Club. It's from 1900. I link this to illustrate that these were upscale clubs, which would have put on an air of respectability Note that admission price was $2 dollars - the menu doesn't appear to list prices for the food, but I would imagine that this puts the admission into the range of $40-60 in today's dollars. At that price range, it would've likely been a suit/tie setting.
There weren't just Single Tax Clubs, there were single tax colonies, such as Fairhope, AL. There was a whole single tax party, which called itself The Commonwealth Land Party. George made a run for mayor of New York City, which he didn't win, but one of his biggest supporters was the Knights of Labor. This is important because of what many of the unions had for reading material. From the Biennial report of the BLS of the State of Colorado: (page 10)
To educate its membership upon sociological industrial and economic questions. Very many of the unions have regular night schools, where the writings of Henry George, Edward Bellamy and other standard authors are taken up chapter by chapter and discussed in a capable and intelligent manner.
Given George's support by the Knights in NYC, it's likely a similar program was instituted there as well.
Even with any controversies that existed because of his ideas, Henry George had a big impact upon the thought of Americans in his day. Even Richard Ely,(one of NRO's Four Horsemen of Progressivism) who was not particularly a fan of George's proposals, wrote the following in his book "Social Aspects of Christianity: And Other Essays": (page 143)
We have also the movement instituted by Henry George, designed to modify a fundamental economic institution, private property in land, and Henry George's name within ten years has become a household word in America, Europe, and Australia, and is not unknown in Asia and Africa.
It is sometimes foolishly asserted by ignorant people that these social and economic movements are not American, but essentially foreign. This is absurd. They are, as pointed out, cosmopolitan, and not national at all, and take them all together it may be doubted whether any country has contributed so much to these social movements as the United States. From every land the wage earning classes are looking to America for inspiration and direction.