In Missouri, the question of how to regulate the carrying of guns — and adjudicate the armed conflicts that sometimes result — is older than the state itself. Lawmakers passed restrictions meant to prevent slave uprisings, and a governor once encouraged the armed expulsion of Mormons. Concealed carry has gone from being banned by the state Constitution, to requiring no permit at all. And while Missouri was a late adopter of “stand your ground” legislation, the new legal protections for self-defense shooters follow a history of residents meting out their own justice with the squeeze of a trigger, as the following timeline shows.

1803: The Louisiana Purchase

Under President Thomas Jefferson, the United States assumes control of 827,000 square miles of untamed territory west of the Mississippi River. The $15 million transaction includes all or part of 15 eventual states, including what becomes the state of Missouri. By 2017, the state’s most prominent city, St. Louis — the “Gateway to the West” — will have the highest homicide rate in the nation.

1818: Missouri’s first weapons laws

The territory’s legislature passes one of Missouri’s first gun regulations, enacting a law barring slaves from carrying or possessing guns, ammunition, clubs, or other weapons. The statute grants whites the right to seize weapons found in slave possession.

1820: The Missouri Compromise

The territory’s representatives push for statehood, but federal officials are reluctant to grant it, fearing that Missouri’s admission to the Union as a slave state will upset the balance of power between free and slave states. To address this concern, Congress passes the Missouri Compromise, which admits Missouri as a slave state and Maine as a free state. But the issue is far from settled.

1833: Extermination order

Tension between residents of Jackson County and the Mormons that have claimed it as sacred ground peaks when a violent mob chases members of the religion from the county. The state of Missouri decides to separate the Mormons from the general population by relocating the former to the newly created Caldwell County. Ongoing tension will lead some Missourians to take up arms against Mormons at the polls when they try to vote. To restore the peace, Governor Lilburn Boggs endorses more violence: His extermination order mandates the expulsion of Mormons by any means necessary, including deadly force.

1861-1865: Guerrillas beget gun bans

Missouri becomes a hotbed for pro-Confederate guerrilla warfare, which state officials combat by passing various firearm restrictions. “In some parts of Missouri, where guerrilla warfare was especially problematic, there were restrictions on the possession of weapons for both loyal and disloyal persons,” says Dennis Boman, professor of history at Lindenwood University. None of the new measures stopped the violence. Missouri is home to about 4,000 guerrilla fighters, a force that eventually requires approximately 60,000 Union troops to subdue.

1874: No hidden weapons allowed

Post-Civil War lawlessness in Missouri leads to a rise in vigilantism. “You had a lot of people fighting who weren’t actually in either army,” says Al Viola, a historian with the Boone County Historical Society. To combat the surge in violence, the state legislature bans concealed weapons in churches, schoolrooms, election polls, courtrooms, and public assemblies. Lawmakers make sure that it is specifically enforced against freed slaves, and thwart their ability to defend themselves, says Kevin Jamison, author of Missouri Weapons and Self-Defense Law. In 1875, the state will effectively ban concealed weapons of any kind, anywhere, for the next 128 years.

1885: Rise of the vigilantes

Nathaniel Kinney, an ex-Union soldier, is frustrated with Missouri’s lawlessness. He and about 100 other men start an armed gang that calls itself the Bald Knobbers. Soon after, Eglinton resident Frank Taylor gets into a dispute with local store owners, trashes their property and, with his brother, shoots the owners, who survive. The brothers turn themselves in, but the Knobbers attack the jail and lynch the Taylors. They leave a note that reads: “Beware! These are the first victims to the wrath of outraged citizens. More will follow.”

1945: State constitution, revised

Lawmakers revise the state constitution of 1875, modernizing the language on the concealed-weapons ban. The clause addressing concealed carry — which previously read, “But nothing herein contained is intended to justify the practice of wearing concealed weapons” — is updated. The new language explicitly bans the practice: ”This shall not justify the wearing of concealed weapons.”

1977: Prelude to the Castle Doctrine

Velma Gardner, a Kansas City resident, shoots and kills her husband in the driveway of their home as he attempts to hit her with his car. Gardner is convicted of manslaughter and sentenced to a year in prison. The courts decide that people may turn to lethal force as a first resort only to defend themselves inside their dwellings; outside them, residents have a “duty to retreat,” which she did not exercise when exiting the front door, approaching the driveway, and opening fire. Thirty years later, the legislature passes the Castle Doctrine, expanding the legal use of deadly force to anywhere on one’s property.

2003: The return of concealed carry

The Missouri House of Representatives overturns the state’s concealed-carry ban after 128 years. Eighty-four of the state’s 162 representatives sponsor the bill. Opponents try to overturn the law, arguing it violates the state constitution. The Missouri Supreme Court says the constitution doesn’t explicitly forbid concealed guns and state lawmakers have the authority to decide who can carry them and under what circumstances. Missouri is one of 46 states allowing concealed carry.

2005: National birth of “stand your ground”

The Florida Legislature passes the nation’s first “stand your ground” law. To critics’ dismay, the new law allows those acting in self-defense to use deadly force in public spaces. By 2017, 24 states will have passed “stand your ground” laws.

2006: Castle Doctrine becomes law in Missouri

Lawmakers introduce and easily pass Senate Bill 62, Missouri’s version of the Castle Doctrine. Without needing to retreat into one’s home, homeowners may use lethal force to defend themselves, family, home, property or vehicle as long as they “occupy” that property. In another change, gun purchasers no longer need a permit to acquire a concealable firearm, a mandate that has been in place since 2004.

2010: Prelude to “stand your ground”

Shauntay Henderson shoots and kills DeAndre Parker outside a Kansas City gas station as he tries to run her down with his truck. Henderson says she feared for her life when she reached for her gun. Acquitted of second-degree murder, she’s convicted of voluntary manslaughter and armed criminal action because she failed to retreat before shooting. The court rules that Missouri residents are entitled to use deadly force if they reasonably believe it is necessary to defend themselves against death, severe injury or “forcible felony.”

2012: Trayvon Martin

George Zimmerman, a neighborhood watch captain in Sanford, Florida, shoots and kills Trayvon Martin, an unarmed black teenager, sparking national outrage and debate over the meaning of self-defense, the use of lethal force and the role of race in gun violence. Though he claimed it was a self-defense shooting, Zimmerman did not invoke “stand your ground.” Nevertheless, the case elevates the specter of “stand your ground.” The following summer, Zimmerman is acquitted of second-degree murder.

2014: Schools and teenagers

The Missouri General Assembly passes a law allowing certified school employees to carry guns on campus and decreases the legal concealed-carry age from 21 to 19. The law is sponsored by Republican Senator Will Kraus. Governor Jay Nixon, a Democrat, vetoes the law but the legislature overrides his decision by a vote of 117 to 39.

2015: “Stand your ground” and permitless carry adopted

Republican Senator Brian Munzlinger, a farmer from northeastern Missouri, introduces a bill to eradicate the “duty to retreat.” A separate provision eliminates need for concealed-carry permits. Again, the law passes easily; again, Nixon vetoes it; again, legislators later overwhelmingly override him. Now anyone in Missouri may carry a concealed weapon in most public places without a permit, and claim immunity in armed confrontations.

2017: The road ahead

Certain areas — like airports and courthouses — remain off-limits to concealed firearms, whether their owner is licensed to carry or not. Uncertainty surrounds the new law in other places, including the state Capitol, where legislators are permitted to carry weapons inside the House and Senate chambers. Colleges may still ban guns on campus. But if Republican Representative Jered Taylor has his way, this too might change. Taylor’s proposed legislation, House Bill 630, was introduced January 17. On April 19, the Standing Committee on Rules voted “do pass.” There have not been any additional actions on the bill.