The small swivel cannon was commonly used on ships and riverboats, as well as in forts, in 18th- and 19th-century America. Captain Clark had one installed on the bow of the keelboat. It would have been mounted on a yoke resembling an oarlock. With the foot of the yoke inserted in a hole on the ship's rail, the wall of a fort, or a stanchion on the bow of the keelboat, the cannon could be swiveled right or left; up or down. Swivel cannons typically have a projecting piece at the back end with a cavity which accepts a dowel to be used as a tiller or handle for guiding the direction of firing without burning the gunner's hands.
The journals do not mention the size of the swivel cannon on the keelboat, but typical swivels of the era would range from 18" to 36" in length, with a bore from one to two inches in diameter. The specimen illustrated here is 22" overall length with a bore of 1-3/4." This bore is quite suitable for accommodating the 16 musket balls Captain Lewis ordered to be loaded during the standoff with the Teton Sioux on September 25, 1804. Fortunately, it wasn't necessary to fire it in anger that day, nor any other day during the entire expedition.
However, the swivel cannon is mentioned frequently in the journals for its usefulness as a signaling instrument. While the keelboat was proceeding upstream, the hunters would be on shore, sometimes a mile or more from the river in pursuit of fresh meat. At the end of the day a blank shot would be fired from the swivel to orient the hunters to the keelboat's location.
It was also handy for other peaceful purposes, such as some sort of celebration. "Two shot were fired from this swivel, followed by a round of small arms, to welcome the New year," wrote Patrick Gass on January 1, 1805.
Being a heavy gun with a severe recoil, the swivel gun was not suitable for use on the canoes. Lewis had the swivel gun buried in the cache made in June 1805 before the portage around the Great Falls. They recovered it on their way home in August of 1806, and soon were able to lighten their load somewhat. "As our swivel could no longer be serviceable to us as it could not be fired on board the largest perogue," wrote Clark on the sixteenth, "we concluded to make a present of it to the Great Chief of the Menetaras (the One Eye) with a view to ingratiate him more Strongly in our favor.... After the council was over the gun was fired and Delivered."
Funded in part by a grant from the National Park Service Challenge Cost Share Program.