Army records are very clear. Col Sylvester Churchill shared his post with Col George Croghan at Fort Churchill Navada. Col George Croghan's nephew William Croghan married Lucy Clark the sister of William Clark the Explorer and partner to Meriwether Lewis.
Larry, I am unfamaliar with your Col Sylvester.What is his descendancy from the English Devon family?
He sounds like an Oxfordshire Churchill rather than a Devon Churchill.What is his descendancy?
We can verify his Origin if you know anyone of his line who would test?