To the Senate and House of Representatives of the United States:
It was reasonably expected that while the limits between the territories of the United States and of Spain were unsettled neither party would have innovated on the existing state of their respective positions. Some time since, however, we learnt that the Spanish authorities were advancing into the disputed country to occupy new posts and make new settlements. Unwilling to take any measures which might preclude a peaceable accommodation of differences, the officers of the United States were ordered to confine themselves within the country on this side of the Sabine River which, by delivery of its principal post, Natchitoches, was understood to have been itself delivered up by Spain, and at the same time to permit no adverse post to be taken nor armed men to remain within it. In consequence of these orders the commanding officer of Natchitoches, learning that a party of Spanish troops had crossed the Sabine River and were posting themselves on this side the Adais, sent a detachment of his force to require them to withdraw to the other side of the Sabine, which they accordingly did.
I have thought it proper to communicate to Congress the letter detailing this incident, that they may fully understand the state of things in that quarter and be enabled to make such provision for its security as, in their wisdom, they shall deem sufficient.
Thomas Jefferson, Special Message Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/203995