Was the Second Ratified to Preserve Slavery?
Some claim the Second Amendment, like the Three-Fifths Compromise, was ratified to preserve slavery. This is only partially true. Both Amendments were “about slavery,” but neither were ONLY about slavery, we explain this stance below. 
TIP: Slaves’ patrols (slaves chained, trained, and armed alongside armed and trained militiamen) were the militia’s of the Second Amendment in the south. In the North they were different. In all cases their purpose was to ensure the law and the security of a free state; unfortunately slavery was legal at the time.
“A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.” – The Second Amendment from the Bill of Rights (1791) which Amends the Constitution (1787).
TIP: See our page on the true meaning of the Second for the long-form overview of everything you need to know based on historical documents and modern intellectual debate.
Slave Patrols and the 2nd Amendment p1. A view on slave patrols by Thom Hartmann (a left-winger), he is joined by historians (which helps keep this video centered). See an opposing view here.
The Truth About Slave Patrols and the Second Amendment
The militia’s of the Second were called “slave patrols” in the South. This is because they included slaves in their ranks and because their main job (aside from being a sort of community police force) was to put down rebellions and uprisings. Many rebellions and uprisings were slave rebellions, and sometimes keeping law and order meant the patrols went after escaped slaves, but this only explains part of the militia’s purpose and militias in the south.
The real reason behind the militias of the Second Amendment is to put down uprisings like Shays’ Rebellion and the Whiskey Rebellion. The well-regulated militia must be ready to be called upon by the state or federal government to do a job similar to what the National Guard or military would do today.
We know this from historical documents, including those which show Patrick Henry (and other founders and politicians at the time) discussing how slaves patrols could be used against southern slave states by the federal government. We also know the purposes of militias and the intentions of the Second because we have The Federalist: No. 29 and No. 46 which discuss militias in general.
So while the Second did help preserve slavery, its intentions weren’t about slaves, self-defense, gun ownership, or other rights (or lack thereof), they were about state and federal government having the power to keep order or “to secure a free state“.
TIP: Despite the above, the Second is today used to justify collective and individual rights and the military and police do the duties of the militias of the Second. I’m no fan of assault weapons or slavery, but based on reading the Bill of Rights, the Federalist papers, and documented letters from America’s founders, there is little room to make the argument that The Second Amendment was ratified ONLY to preserve slavery. That is a myth.
FACT: The Three-Fifths Compromise was also, like the Second and other amendments, in part ratified due to reasons that were related to slavery. The argument was over whether, and how, slaves should be counted when determining a state’s total population for legislative representation and taxing purposes. The eventual three-fifths compromise declared that three-fifths of a person for could be counted for taxation etc. This led to the dominance of the Southern bloc and thus the preservation of slavery until Lincoln. As the result, slave states had more seats in Congress, and one third more electoral votes, than if the compromise was not reached. It was largely the progressive Federalist/Whig/soon-to-be-Republicans of the time who opposed the compromise for political reasons, despite the fact that they were in many ways the Civil Rights party of their day. (The parties switched platforms over time, i.e. why Lincoln was a pro-north moderate-progressive).
“Much has been said of the impropriety of representing men who have no will of their own…. They are men, though degraded to the condition of slavery. They are persons known to the municipal laws of the states which they inhabit, as well as to the laws of nature. But representation and taxation go together…. Would it be just to impose a singular burden, without conferring some adequate advantage?” — Alexander Hamilton (Hamilton is of the lineage of Lincoln in regards to party politics. They are both of the line that falls out of power due to the 3/5 compromise, which favors the southern-pro-slavery Democrats, who are today’s post-64′ Republicans in terms of at the very least geographic location).
The Three-Fifths Compromise Explained: US History Review.