Over a period of 15 years, from 1774 to 1789, the Continental Congress underwent a profound evolution. Starting out as a temporary group that met to address American colonists’ issues with British rule, it morphed into the de facto government of the 13 colonies, and ultimately into an official governing body of the United States.

These different phases of the congress are often referred to as the First Continental Congress, Second Continental Congress and Confederate Congress. Here are the major achievements of each.

The First Continental Congress began under British rule in September 1774. Comprised of 56 delegates from 12 of the original 13 colonies, the group met in Philadelphia and lasted less than two months. It focused mainly on how to respond to the British Parliament’s passage of the Intolerable Acts—also known as the Coercive Acts—a series of repressive acts designed to restore order to Boston after the Tea Party and punish the colonists for their bold insurrection. During its short meeting time, the Continental Congress compiled a list of grievances that it sent to Britain’s then-ruler, King George III. It also adopted the Articles of Association, which initiated a boycott of British goods by the colonies.

The Articles of Association stand as the First Continental Congress’s most important accomplishment, says Benjamin H. Irvin, a history professor at Indiana University Bloomington and author of Clothed in Robes of Sovereignty: The Continental Congress and the People Out of Doors. In addition to the boycott, the document authorized the creation of local committees to help with the transfer of power between Britain and the colonies.

Unlike later versions of the Continental Congress, the first one didn’t see itself as a governing body. The British Empire was still the recognized governing authority, and the Articles of Association that the First Continental Congress issued was not a law. Even so, “the Continental Congress did take measures to prepare the colonists for the possible overthrow of British authority,” Irvin says.

“The Congress endorsed the Suffolk Resolves, in which the people of Suffolk County, Massachusetts, determined ‘to acquaint themselves with the art of war,’” he says. And by calling on local communities to establish committees of inspection in the Articles of Association, “Congress readied the American people to throw off British rule and establish local government.”

The Second Continental Congress started in May 1775, less than a month after the first Revolutionary War battles at Lexington and Concord. This time, the Continental Congress’s role was different, as it became the de facto government of the 13 colonies during their war with the British Empire.

“The delegates wasted no time deliberating the nature or extent of their authority; instead, they convened in the spirit of a council of war,” says Irvin. The Continental Congress established an army, a navy and a post office, and issued currency. “In this manner, and without hesitation, the Continental Congress began to assume legislative and executive responsibility.”

Many of the men who attended the First Continental Congress returned for the second, including George Washington, Patrick Henry and cousins John and Samuel Adams. Newcomers included Thomas Jefferson, Benjamin Franklin, James Madison and John Hancock.

The Second Continental Congress’s most significant achievement? The adoption of the Declaration of Independence, which it ratified on July 4, 1776.

“The establishment of the Continental Army, the printing of the continental currency, the recommendation that the colonies draft new constitutions, the pursuance of an alliance with France, the disavowal of parliament—: these were the works by which U.S. independence was achieved,” he says.

The Second Continental Congress also created the first U.S. constitution, known as the Articles of Confederation, which took effect in 1781 while the war was ongoing. (It ended in 1783.) The Constitution made the Continental Congress an official governing body of the United States. But although the Continental Congress continued to operate under the same name and with many of the same members, the Articles of Confederation placed limits on what it was able to do.

The Confederation Congress, as many historians refer to it, had very limited powers compared with the U.S. Congress we have today. The Confederation Congress couldn’t tax Americans and, in many cases, needed nine of the 13 states to approve legislation before a bill could pass.

This Confederation Congress did make its mark, though. It chartered the first U.S. bank; and more significantly, it called for the seizure of Native land through measures like the Northwest Ordinance of 1787.

“The most consequential actions of the Confederation Congress were the land ordinances of the 1780s,” says Irvin. “These ordinances encouraged the westward migration of European Americans, who seized lands inhabited by Indigenous peoples, made war against them and ultimately lobbied for their forcible removal.”

Members who served terms on the Confederation Congress included James Madison and Alexander Hamilton, who were also two of the 55 delegates that attended the Constitutional Convention in Philadelphia in 1787. The members of that convention drafted a new constitution that, when it became law in 1789, replaced the Articles of Confederation and disbanded the Confederation Congress, replacing it with the U.S. Congress.