Just previous to the start of the Civil War; as southern states began to secede, the Democratic Mayor of New York City, Fernando Wood proposed that the city secede. Wood who was consider to be the most unethical mayor in the city’s history, suggested the city become a sovereign city state called Free City of Tri-Insula. It would have included Long Island, Manhattan, and Staten Island. Wood addressed the Common Council on January 6th 1861 in which he articulated a commiseration with the seceded southern states, stating that the city would find a great profit in maintaining cotton shipping.
The idea of seceding from the United States was to extreme for the Council, and after the south bombed Fort Sumter in April 1861 it fell apart. As a side note though the upstate New York town of Town Line did vote to secede from the Union, and did not officially rejoin until 1946.