Although the constitution does not mention the issue of secession, The Supreme Court has consistently interpreted the Constitution to be an "indestructible" union. The states cannot leave the Union. There is no legal basis a state can point to for unilaterally seceding.
The black death effect society by a series of religious, social, and economic upheavals. it was one of the most devastating pandemics in human history, peaking in europe between 1347 and 1350 with 30% to 65% of the population killed.
