To the House of Representatives of the United States:
For some weeks past I have had reason to expect by every mail from New Orleans information which would have fully met the views of the House of Representatives, expressed in their resolution of December 31, on the subject of a post-road from the city of Washington to New Orleans; but this being not yet received, I think it my duty without further delay to communicate to the House the information I possess, however imperfect.
Isaac Briggs, one of the surveyors-general of the United States, being about to return in July last to his station at Natchez, and apprised of the anxiety existing to have a practicable road explored for forwarding the mail to New Orleans without crossing the mountains, offered his services voluntarily to return by the route contemplated, taking as he should go such observations of longitude and latitude as would enable him to delineate it exactly, and by protraction to show of what shortenings it would admit. The offer was accepted and he was furnished with an accurate sextant for his observations. The route proposed was from Washington by Fredericksburg, Cartersville, Lower Sauratown, Salisbury, Franklin Court-House in Georgia, Tuckabachee, Fort Stoddert, and the mouth of Pearl River to New Orleans. It is believed he followed this route generally, deviating at times only for special purposes, and returning again into it. His letters, herewith communicated, will shew his opinion to have been, after completing his journey, that the practicable distance between Washington and New Orleans will be a little over 1,000 miles. He expected to forward his map and special report within one week from the date of his last letter, but a letter of December 10, from another person, informs me he had been unwell, but would forward them within a week from that time. So soon as they shall be received they shall be communicated to the House of Representatives.
Thomas Jefferson, Special Message Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/203755