1To Thomas Jefferson from Isaac Briggs, 9 January 1807 (Jefferson Papers)
Washington City 9 of the 1 mo 1807
2To Thomas Jefferson from Isaac Briggs, 20 October 1808 (Jefferson Papers)
Washington City 20 of the 10 mo 1808.
3Isaac Briggs to Thomas Jefferson, 16 February 1816 (Jefferson Papers)
...exploring and ascertaining the topography of a Post-route from Washington City to
4Isaac Briggs to Thomas Jefferson, 30 March 1816 (Jefferson Papers)
Washington City,
5Isaac 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.
6Isaac Briggs to Thomas Jefferson, 21 May 1817 (Jefferson Papers)
”; franked; postmarked Washington City, 21 May.