Using the pseudonyms Algernon Sydney and Epaminondas many of his writings, defending Jeffersonian principles, were published in many pamphlets.

A staunch supporter of Thomas Jefferson, Granger was appointed as Postmaster General at the start of his term in 1801.

After leaving Washington, D.C., Granger settled in Canandaigua, New York, where he built a homestead that would be "unrivaled in all the nation" from which he could administer the many land tracts he had acquired farther to the west.

He became a member of the New York Senate and continued to be influential in politics and law including being a key figure in the Erie Canal project.

[6] Together, they were the parents of three sons, including:[3] Ill health forced him to retire early in 1821 and he died the next year on December 31, 1822.