Final answer:
The event that signaled the need to replace the Articles of Confederation was Shays' Rebellion, a farmer uprising in Massachusetts. This highlighted the inefficacy of the Articles in dealing with civil unrest and federal needs, leading to the drafting of the United States Constitution.
Step-by-step explanation:
The sign that the Articles of Confederation had to be replaced was crystalized with the event known as Shays' Rebellion.
This rebellion, which took place in 1786, was led by Massachusetts farmer Daniel Shays and other Revolutionary War veterans who were distraught over the potential loss of their farms due to heavy debt and high taxes. The inability of the government under the Articles of Confederation to effectively quell the rebellion demonstrated the need for a stronger federal government.
The rebellion caused widespread panic among the nation's elite and the government of Massachusetts, which highlighted the weaknesses of the Articles. With no power to raise an army, the national government was unable to assist.
Eventually, Massachusetts had to rely on local militias and privately funded armies to stop the uprising. This inadequacy prompted calls for revision and strengthening of the national government, culminating in the Constitutional Convention of 1787.
The key issue was that the Articles provided insufficient power to the national government, especially in matters of defense and interstate commerce. It became increasingly clear that a new framework was needed, leading to the drafting and ratification of the United States Constitution, which replaced the Articles of Confederation in 1787.