In maintaining peace after WWI and to create the League of Nations.
Aside from a general curiosity about space, the United States wanted to go to space because the Russians were trying to get there too, and we were in a "cold" war with them.
Water routes had the advantage over land because, water was a faster transportation than having to walk. Also it did not tire out the men so when they hit shore they were able to walk and not be tired. Then water route was also faster because when trying to ship supply's it is faster than trying to carry it where it needs to go.
