Most of the young Americans who journeyed to Oz in L. Frank Baum's books were girls, with Button-Bright being the major exception. In Ruth Plumly Thompson's books, however, more American boys made their way into Oz. The first such was Bobbie Downs, renamed Bob Up by his companion Notta Bit More. He is a sad, solemn boy, raised in a Dickensian sort of orphanage that didn't even allow laughing. Like Notta, he's a bit over the top, so it's not too surprising that Thompson never used him in a major role after that. She does much better with her second American child character, Peter Brown. He appears in three of her books, and his last name actually isn't mentioned until the last of these. I've already said a bit about him in this post, but I really didn't go into much detail. I'm not sure we ever find out what happened to Peter's parents, but he lives with his grandfather in Philadelphia, Thompson's own hometown. He is an active, athletic kid, primarily interested in baseball, but also interested in other outdoor pursuits. He has been on camping trips, and knows how to milk a goat and prepare simple meals. Peter is quite concerned with how his peers view him, and has some typically masculine aspirations, being secretly excited at the prospect of being a Nome general and a pirate. While I'm not sure the jock stereotype existed in the twenties, and Peter doesn't come across as anti-intellectual (and he's read an Oz book before visiting the magical country), he still comes across as a little too typical-boyish for me to identify with him very much.
Right in the midst of the books with Peter as a protagonist comes another boy hero, known as Speedy. His real name is William, but his last name is never stated. He lives with his uncle, who appears to have been largely based on William J. Hammer, a friend of Thompson's father whom she called "Uncle Billy." In Speedy in Oz, it is revealed that Speedy's Uncle Billy's full name is William J. Harmstead, and that Speedy was named after him. Ruth Waara's Umbrella Island in Oz gives Speedy the last name Harmstead as well, while March Laumer calls him William Rapidan. Speedy's parents died while exploring the South Seas, so he is now in the custody of Uncle Billy, and dwelling in Garden City, Long Island. Like Peter, he is quite active, and in fact his nickname comes partially from his own skill at baseball. Uncle Billy is a scientist and inventor, however, and some of his intellectual interests seem to have rubbed off on his nephew. While Speedy finds paleontology a boring idea, he comes to temporarily serve as a wizard's assistant, a job that I'm not sure Peter would have wanted. When The Yellow Knight of Oz was up for discussion, J. L. Bell made another interesting observation, which is that Peter never really leaves his masculine comfort zone. His only female companion, aside from the Bananny Goat who is written out of the story rather quickly, is the somewhat tomboyish Scraps. Speedy, on the other hand, has female companions in both of his adventures, and he develops crushes on both of them. I suppose you could say Speedy is like Peter with stronger hormones, or something like that.
The fates of both boys remain up in the air, which I suppose is appropriate for Peter, who mentions more than once that he wants to be a pilot. This doesn't necessarily mean anything, though, as a lot of children have career aspirations that they don't actually see through when they grow up. As for Speedy, there's a strong hint at the end of his own book that he will eventually return to Umbrella Island and marry the princess, but there's no official confirmation that this ever came to pass. Assuming the two of them didn't relocate to Oz or elsewhere before the United States entered World War II, they're both of the right age to have served in the war. Speedy has its title character actually considering joining the Navy, but again, who knows whether this ever actually happened? I like to think that people who have visited Oz remain somehow connected to the land, so I doubt either character's fairyland adventures ended even if they did decide to remain in the Great Outside World and become adults.
So, since Thompson's American boy protagonists improved throughout her term as Royal Historian of Oz, does that hold true for the books she had published later? Unfortunately, not really. Tompy Terry from Yankee is a prodigy at both marching band AND sports, giving the impression of someone who is just too perfect. Enchanted Island's David Perry is pleasant enough, but we never really get that much of a sense of his character. He plays hockey and likes dogs better than cats, but those are minor details.