1. The character is uncle sam, the representation of the United States in human form.
2. The man symbolizes the United States gradually becoming more of a world power, both internally and externally (socially and by show of force).
3. The artist isn't exactly trying to prove a point. Instead the author just wants to visualize the US expansion up until the 20th century, making the man bigger and bigger the more territory is gained.
4. The result is that the United States has come from being nothing but a rebellious colony to a recognized world power, but not exactly THE world power. It has become wealthy because of the land it possesses, such as the Eastern U..S (trade & massive industrial space), the panama canal (maritime control), and the western U.S. (trade with China and Japan, gold).
5. Based just on how the look of Uncle Sam progresses, it seems the author is against U.S. imperialism to some extent. Some could perceive Uncle Sam as looking like the typical greedy tycoon who only cares about wealth and power rather than the well being of those under him.
