Final answer:
The plan proposed at the Philadelphia Convention for a Congress with representation based on population was the Virginia Plan.
Step-by-step explanation:
At the Philadelphia Convention, the proposed plan to create a Congress where representation was distributed according to population was called the Virginia Plan. The Virginia Plan favored larger states with its proposition for a bicameral legislature with a lower and upper house, with representation in both houses based on state population. This contrasted with the New Jersey Plan, which proposed a unicameral legislature with equal representation for all states, regardless of size.