In addition he founded his own firm which he called T. A. Marshall Co. His party affiliation is uncertain because the sources are contradictory in this question.
According to the Political Graveyard he was a delegate to the Republican National Convention in 1860, which nominated Abraham Lincoln for the Presidency.
In his function as President of the State Senate Marshall replaced Wood as acting Lieutenant Governor.
His term ended on 14 January 1861 when his successor Francis Hoffmann was inaugurated.
During the American Civil War Marshall was a Colonel in the Union Army.