Norman,

Not a Northern State, but New York City threatened secession. I read about this many years ago and thought it humorous. Here's a paragraph about the proposed secession of New York City from Wikipedia.

In the period of national crisis immediately preceding the American Civil War, Democratic Mayor Fernando Wood, widely considered the most corrupt in the city's history, proposed the secession of the city as a sovereign city-state to be called the Free City of Tri-Insula (Tri-Insula meaning "three islands" in Latin), and incorporating Manhattan, Long Island and Staten Island. In an address to the city's Common Council on January 6, 1861, Mayor Wood expressed a Copperhead sympathy with the threatened seceding states and a desire to maintain profitable cotton shipping, confidence that the city-state would prosper on the import tariffs that then supplied 2/3 of the Federal revenues, and especially dissatisafaction with the state government at Albany. But the idea of leaving the United States proved too radical even in the turmoil of 1861 and was poorly received, especially after the Southern bombardment of Fort Sumter starting on April 12. The war, and especially conscription, was nevertheless often unpopular in the city, sparking the deadly New York Draft Riots.

Jim Martin