I did a little research and found that the US Navy did have some gun boats in WW1, such as the USS Atalanta, shown here:
Here's another small gunboat, Subchaser #57, that was part of the “Splinter Fleet”. These 110-foot boats were small but had a lot of heart.
I could not find any pre-made models for these WW1 gunboats, especially in 1/56th scale. So I took the following plastic model of a WW2 PT boat and modified it.
The whole boathouse was too far forward on the model, so I cut it out, made a new deck and glued it back on much further to the stern. I also converted the machine gun turret into a WW1-era smoke stack, remove all the electronics and cut it down to the "water line". Here is how it turned out:
I also had to re-base some of my sailor because having grass bases on the deck of the ship looked weird.
So, it is probably not super historically accurate, but I feel that it is a fairly close resemblance to the pictures shown above and will work well in our Back of Beyond war gaming.