Why did some Federalists respond to the Louisiana Purchase by plotting to secede from the Union?

They opposed it because they suspected that new states formed in the Louisiana Territory would be Republican and thus jeopardize the balance of power. Some Federalists planned to secede from the Union.

saint clair’s defeat, (november 4, 1791), one of the worst defeats ever suffered by u.s. forces in indian warfare, precipitated by british-indian confrontation with settlers and militia in the northwest territory following the american revolution. despite specific provisions in the treaty of 1783 for the evacuation of its forts on the northwestern border, britain had failed to yield these lucrative fur-trading posts. in hopes of reclaiming lost hunting grounds with british support, a northwest indian confederation was gradually molded between 1785 and 1787, consisting mainly of shawnee, delaware, ottawa, iroquois, ojibwa, miami, and potawatomi. kentucky frontiersmen reacted to this threat by initiating raiding parties on native villages as early as 1788, and indian warfare flared up the following year.

studies show tha in 7.5 billion years from now, the expanding sun will engulf, and destroy, the earth.