Answer:
The most significant accomplishment of the Second Continental Congress was the formal adoption of the Declaration of Independence on July 4, 1776.
Step-by-step explanation:
The colonies organized the Second Continental Congress (delegates from each of the 13 colonies) because the grievances that they outlined to the Biritish government in the First Continental Congress were not taken seriously. As their voices were still not heard and more British troops were sent to the colonies after declaring them "in rebellion", they realized they would have to declare independence and fight in war or otherwise be executed for treason. Among the delegates was the main author of the Declaration of Independence, Thomas Jefferson. This is how the American Revolutionary War started.