Governor Edward Coles appointed Blackwell Illinois Secretary of State on April 2, 1823.
Blackwell's goal in the position was to prevent a constitutional convention in which pro-slavery forces could reverse Illinois' de jure status as a free state.
This goal, achieved in part by Blackwell's control of the Illinois Intelligencer, was accomplished when the referendum failed.
[1] After his time as Secretary of State, Blackwell returned to the Illinois House of Representatives for the 4th General Assembly which commenced November 15, 1824.
[2] On January 2, 1826, he was elected Speaker of the Illinois House of Representatives to replace Thomas Mather who resigned to take a job to locate a military road.