Hartford Convention
The federal government’s decision to commence war with Britain in the War of 1812 was greatly problematic to members of the Federalist party, who favored maintaining peaceful ties between Britain and the United States for the sake of the economy. Thus, delegates of the Federalist Party convened in Connecticut during the winter of December 14, 1814 to discuss the growing power of the federal government. They requested for new reforms in the Congress such as the removal of the three fifths compromise to amplify the voices of the slave states, and the requirement of a two-thirds majority vote to declare war.
http://global.britannica.com/media/full/256148/122536