In addition to foot soldiers, America brought a handful of 14 inch rail guns to the Allied war effort of WW I.
Here is pic of Mk I gun. Before the gun can be fired the car must be lifted off the 4- three axle bogies with jack screws. Then, a 9 foot deep pit was dug beneath the mid-section and recoil "sleepers" anchored into
earth. These engaged car frame to absorb recoil. The pit had a second function---it allowed gun elevation to
around 60 degrees. The breech filled the pit.
Mk II gun
Heavier gun with higher gun mount allowed use of french system of hydraulic recoil and rail car movement
rearwards of about 50 feet. 20 axle carrier. No gun pit required.
10 min video of Mk I gun in France
Navy 14 Inch Railway Guns in France, 1918 - YouTube
these guns were almost certainly products of Watervliet Arsenal.
[this statement is incorrect. the 14 inch naval guns were constructed at the Washington Navy Yard---as PM member old_dave points out]