Final answer:
The first significant event that took place in Philadelphia was the 3) First Continental Congress in 1774, with subsequent events such as the signing of the Declaration of Independence and the 2) Constitutional Convention (also known as the 4) Philadelphia Convention) occurring later.
Step-by-step explanation:
Events in Philadelphia's Colonial History
The first significant event that took place in Philadelphia relevant to the options provided was the 3) First Continental Congress, which convened in September 1774.
During this congress, colonial leaders from 12 of the 13 colonies met to discuss a unified response to the British Parliament's policies.
The other events listed, including the signing of the Declaration of Independence, the 2) Constitutional Convention, and the similarly named 4) Philadelphia Convention, took place after the First Continental Congress.
The Philadelphia Convention is another name for the 1787 Constitutional Convention, where the U.S. Constitution was drafted, effectively replacing the Articles of Confederation.