<em>A bicameral or two-house Congress was a feature of the Virginia plan presented at the Constitutional convention.</em>
Drafted by James Madison, the Virginia Plan established a bicameral legislature. During the Constitutional Convention of 1787, the Virginia plan suggested that the states should be represented depending on the number of population. Another interesting element included in the Virginia plan was the creation of three branches of government: a legislative, an executive and a judicial branch.
I remember learning that this is because of the unintelligent. It is because they want this to be directed to people who need to know what they are doing.