1Isaac Briggs to Thomas Jefferson, 16 February 1816 (Jefferson Papers)
...exploring and ascertaining the topography of a Post-route from Washington City to
2Isaac Briggs to Thomas Jefferson, 30 March 1816 (Jefferson Papers)
Washington City,
3Isaac Briggs to Thomas Jefferson, 7 May 1816, with Postscript by Mary B. Briggs (Jefferson Papers)
...present residence, during a second journey I have made to Washington City. I returned yesterday.