Anti-federalists were a group of colonists concerned a strong central government would one day overwhelm the populace and become tyrannical. The group had several well known and respected leaders such as Patrick Henry and Samuel Adams. The group played an important role in the ratification of the Constitution. They were opposed to it and attempted to stop it infamously in Pennsylvania. To prevent a quorum the anti-federalists refused to attend the state assembly. They were found, forced to the state house and locked inside to complete the vote.
When the amendments to the Constitution were proposed, the anti-federalists saw this as a chance to achieve some victory despite their defeat. The anti-federalists and Thomas Jefferson saw the amendments as a way to limit the power of the government. The Bill of Rights was the first move to satisfy the anti-federalists and assuage the fears of many the power of the government might grow too big. The most important amendment was the Tenth Amendment which limited the power of the federal government. The amendment provides the powers not delegated to the federal government would be retained by the states. The anti-federalists felt this was essential to ensure the states bound together would always be more powerful than the federal government.