What plan proposed a two-house legislature with the upper house having equal representation of the states?

The plan that proposed a two-house legislature with the upper house having equal representation of the states is known as the New Jersey Plan. Introduced in 1787 during the Constitutional Convention, it aimed to amend the Articles of Confederation rather than replace them. The plan suggested that each state would have an equal number of representatives in the Senate, ensuring that smaller states had an equal voice in the legislative process alongside larger states.