Formation of a bicameral legislature was the most significant contribution made by John Adams to the U.S. Constitution.
Explanation:
John Adams advocated the need of a bicameral legislatures i.e., the Congress consisting of two houses (upper house and lower house) as according to him, the upper house, if adopted a bicameral legislature, can keep a check on the authority exercised by the majorities in the lower house.
In some cases, the two-chamber system may consist of two parliamentary chambers. The general goal of the legislature with two chambers is to represent both nationals and state legislators at federal level or in the central government of a country or nation.