What was the main accomplishment of the Second Continental Congress

The Second Continental Congress managed the colonial war effort, and moved towards independence, adopting the United States Declaration of Independence on July 4, 1776.

According to my history book on the early U. S., they also had drew up the first plan of national government, The Articles of Confederation. However, this may not be considered the 'Big Accomplishment' you are looking for, as this form of government lasted for a short time (less than 20 years).