Taggart is listed as a merchant at 4 Chestnut Street, Philadelphia, in James Hardie's 1793 Directory. Also, John Taggart's store is listed at North Water Street, East Side 11 in Hogan's 1795 Directory. Taggart is additionally listed at 5 and 11 North Water Street in the directories of 1798-1800. By 1801, he is listed at 7 North Water Street where he remained at least through 1813.
The first correspondence between Taggart and Jefferson is dated May 2, 1805. Most of the correspondence between these two concerns paint supplies, i.e. underground white lead, pigments, linseed oil, stone ocher, turkey umber, etc. The last 5 letters between the two involve a request by Taggart for Jefferson's recommendation on behalf of Taggart's son to the Secretary of the Navy. The matter was left hanging in the last letter between the two, as Jefferson had decided to avoid entanglements of this nature, and the Secretary of the Navy had changed since he had been in office. It is not certain if Jefferson's failure to help Taggart in this matter soured their relationship, or if Jefferson simply no longer needed paint supplies, but no further letters passed between Taggart and Jefferson after this incident.
A note in the Maryland Journal and Baltimore Daily Advertiser, of October 15, 1790 states that a John Tagart of Philadelphia married a Miss Polly Williamson of Baltimore Co. Whether this is the same John Taggart or not is not known.