Infographic illustrating the attributes of the average American gun owner.
The United States has 120.5 guns per 100 people, or about 393,347,000 guns, which is the highest total and per capita number in the world. 22% of Americans own one or more guns (35% of men and 12% of women). America's pervasive gun culture stems in part from its colonial history, revolutionary roots, frontier expansion, and the Second Amendment, which states: "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."
Proponents of more gun control laws state that the Second Amendment was intended for militias; that gun violence would be reduced; that gun restrictions have always existed; and that a majority of Americans, including gun owners, support new gun restrictions.
Opponents say that the Second Amendment protects an individual’s right to own guns; that guns are needed for self-defense from threats ranging from local criminals to foreign invaders; and that gun ownership deters crime rather than causes more crime.
Guns in Colonial and Revolutionary America
Guns were common in the American Colonies, first for hunting and general self-protection and later as weapons in the American Revolutionary War.  Several colonies' gun laws required that heads of households (including women) own guns and that all able-bodied men enroll in the militia and carry personal firearms. 
Some laws, including in Connecticut (1643) and at least five other colonies, required "at least one adult man in every house to carry a gun to church or other public meetings" in order to protect against attacks by Native Americans; prevent theft of firearms from unattended homes; and, as a 1743 South Carolina law stated, safeguard against "insurrections and other wicked attempts of Negroes and other Slaves."  Other laws required immigrants to own guns in order to immigrate or own land. 
The Second Amendment of the US Constitution was ratified on Dec. 15, 1791. The notes from the Constitutional Convention do not mention an individual right to a gun for self-defense.  Some historians suggest that the idea of an individual versus a collective right would not have occurred to the Founding Fathers because the two were intertwined and inseparable: there was an individual right in order to fulfill the collective right of serving in the militia. 
Although guns were common in colonial and revolutionary America, so were gun restrictions. Laws included banning the sale of guns to Native Americans (though colonists frequently traded guns with Native Americans for goods such as corn and fur); banning indentured servants (mainly the Irish) and slaves from owning guns; and exempting a variety of professions from owning guns (including doctors, school masters, lawyers, and millers). 
An 1879 sign in Dodge City, KS prohibiting the carrying of guns. Source: Saul Cornell, "What the 'Right to Bear Arms' Really Means," www.salon.com, Jan. 15, 2011
A 1792 federal law required that every man eligible for militia service own a gun and ammunition suitable for military service, report for frequent inspection of their guns, and register his gun ownership on public records.  Many Americans owned hunting rifles or pistols instead of proper military guns, and even though the penalty fines were high (over $9,000 in 2014 dollars), they were levied inconsistently and the public largely ignored the law. 
State Gun Laws: Slave Codes and the "Wild West"
From the 1700s through the 1800s, so-called "slave codes" and, after slavery was abolished in 1865, "black codes" (and, still later, "Jim Crow" laws) prohibited black people from owning guns and laws allowing the ownership of guns frequently specified "free white men."  For example, an 1833 Georgia law stated, "it shall not be lawful for any free person of colour in this state, to own, use, or carry fire arms of any description whatever… that the free person of colour, so detected in owning, using, or carrying fire arms, shall receive upon his bare back, thirty-nine lashes, and that the fire arm so found in the possession of said free person of colour, shall be exposed for public sale." 
Despite images of the "Wild West" from movies, cities in the frontier often required visitors to check their guns with the sheriff before entering the town.  In Oct. 1876, Deadwood, Dakota Territory passed a law stating that no one could fire a gun without the mayor's consent.  A sign in Dodge City, Kansas in 1879 read, "The Carrying of Fire Arms Strictly Prohibited."  The first law passed in Dodge City was a gun control law that read "any person or persons found carrying concealed weapons in the city of Dodge or violating the laws of the State shall be dealt with according to law." 
Federal Gun Laws in the 1900s
The St. Valentine's Day Massacre on Feb. 14, 1929 in Chicago resulted in the deaths of seven gangsters associated with "Bugs" Moran (an enemy of Al Capone) and set off a series of debates and laws to ban machine guns.  Originally enacted in 1934 in response to mafia crimes, the National Firearms Act (NFA) imposes a $200 tax and a registration requirement on the making and transfer of certain guns, including shotguns and rifles with barrels shorter than 18 inches ("short-barreled"), machine guns, firearm mufflers and silencers, and specific firearms labeled as "any other weapons" by the NFA.  Most guns are excluded from the Act.
The Federal Firearms Act of 1938 made it illegal to sell guns to certain people (including convicted felons) and required federal firearms licensees (FFLs; people who are licensed by the federal government to sell firearms) to maintain customer records.  This Act was overturned by the 1968 Gun Control Act.
Former Reagan Press Secretary Jim Brady sits by President BIll Clinton as Clinton signs the Brady Bill into law on Nov. 30, 1993 Source: Eric Bradner, "Hinckley Won't Face New Charges in Reagan Press Secretary's Death," www.cnn.com, Jan 3, 2015
In 1968 the National Firearms Act was revised to address constitutionality concerns brought up by Haynes v. US (1968), namely that unregistered firearms already in possession of the owner do not have to be registered, and information obtained from NFA applications and registrations cannot be used as evidence in a criminal trial when the crime occurred before or during the filing of the paperwork. 
On Oct. 22, 1968, prompted by the assassinations of President John F. Kennedy (1963), Malcolm X (1965), Martin Luther King, Jr. (1968), and Robert F. Kennedy (1968), as well as the 1966 University of Texas mass shooting, President Lyndon B. Johnson signed the Gun Control Act of 1968 (GCA) into law.  The GCA regulates interstate gun commerce, prohibiting interstate transfer unless completed among licensed manufacturers, importers, and dealers, and restricts gun ownership. 
The Firearm Owners' Protection Act of 1986 (FOPA) revised prior legislation once again.  The Act, among other revisions to prior laws, allowed gun dealers to sell guns away from the address listed on their license; limited the number of inspections the Bureau of Alcohol, Tobacco, and Firearms (now the Bureau of Alcohol, Tobacco, Firearms and Explosives) could perform without a warrant; prevented the federal government from maintaining a database of gun dealer records; and removed the requirement that gun dealers keep track of ammunition sales. 
The Brady Handgun Violence Prevention Act of 1993 (also called the Brady Act) was signed into law on Nov. 30, 1993 and required a five-day waiting period for a licensed seller to hand over a gun to an unlicensed person in states without an alternate background check system.  The five-day waiting period has since been replaced by an instant background check system that can take up to three days if there is an inconsistency or more information is needed to complete the sale.  Gun owners who have a federal firearms license or a state-issued permit are exempt from the waiting period. 
The Federal Assault Weapons Ban (Public Safety and Recreational Firearms Use Protection Act), part of the Violent Crime Control and Law Enforcement Act of 1994, was signed into law by President Bill Clinton on Sep. 13, 1994. The ban outlawed 19 models of semi-automatic assault weapons by name and others by "military features," as well as large-capacity magazines manufactured after the law's enactment.  The ban expired on Sep. 13, 2004 and was not renewed due in part to NRA lobbying efforts. 
Federal and State Gun Laws in the 2000s
Protection of Lawful Commerce in Arms Act and Child Safety Lock Act of 2005 was enacted on Oct. 26 by President George W. Bush and gives broad civil liability immunity to firearms manufacturers so they cannot be sued by a gun death victim's family.  The Child Safety Lock Act requires that all handguns be sold with a "secure gun storage or safety device."
The National Instant Criminal Background Check System (NICS) Improvement Amendments Act of 2007 was enacted as a condition of the Brady Act and provides incentives to states (including grants from the Attorney General) for them to provide information to NICS including information on people who are prohibited from purchasing firearms.  The NICS was implemented on Nov. 30, 1998 and later amended on Jan. 8, 2008 in response to the Apr. 16, 2007 Virginia Tech University shooting so that the Attorney General could more easily acquire information pertinent to background checks such as disqualifying mental conditions. 
On Jan. 5, 2016, President Obama announced new executive actions on gun control. His measures take effect immediately and include: an update and expansion of background checks (closing the "gun show loophole"); the addition of 200 ATF agents; increased mental health care funding; $4 million and personnel to enhance the National Integrated Ballistics Information Network (used to link crimes in one jurisdiction to ballistics evidence in another); creating an Internet Investigations Center to track illegal online gun trafficking; a new Department of Health and Human Services rule saying that it is not a HIPAA violation to report mental health information to the background check system; a new requirement to report gun thefts; new research funding for gun safety technologies; and more funding to train law enforcement officers on preventing gun casualties in domestic violence cases. 
Open carry activists in Texas pose with rifles. Source: TruthVoice, "Texas Set to Approve Open Carry of Pistols," www.truthvoice.com, Apr. 19, 2015
In addition to federal gun laws, each state has its own set of gun laws ranging from California with the most restrictive gun laws in the country to Arizona with the most lenient, according to the Law Center to Prevent Gun Violence and the Brady Campaign's "2013 State Scorecard." . 43 of 50 states have a "right to bear arms" clause in their state constitutions. 
The most common state gun control laws include background checks, waiting periods, and registration requirements to purchase or sell guns.  Most states prevent carrying guns, including people with a concealed carry permit, on K-12 school grounds and many states prevent carrying on college campuses.  Some states ban assault weapons. 
Gun rights laws include concealed and open carry permits, as well as allowing gun carry in usually restricted areas (such as bars, K-12 schools, state parks, and parking areas).  Many states have "shoot first" (also called "stand your ground") laws.  Open carry of handguns is generally allowed in most states (though a permit may be required). 
Collective v. Individual Right: Guns and the Supreme Court
Until 2008, the Supreme Court repeatedly upheld a collective right (that the right to own guns is for the purpose of maintaining a militia) view of the Second Amendment, concluding that the states may form militias and regulate guns. 
The first time the Court upheld an individual rights interpretation (that individuals have a Constitutional right to own a gun regardless of militia service) of the Second Amendment was the June 26, 2008 US Supreme Court ruling in DC v. Heller. The Court stated that the right could be limited: "There seems to us no doubt, on the basis of both text and history, that the Second Amendment conferred an individual right to keep and bear arms. Of course the right was not unlimited… Thus we do not read the Second Amendment to protect the right of citizens to carry arms for any sort of confrontation, just as we do not read the First Amendment to protect the right of citizens to speak for any purpose." 
A portrait of General Ambrose Burnside, first president of the NRA Source: John Hathorn, "General Ambrose E. Burnside, May 23-1924-September 13, 1881," www.history.ncsu.edu (accessed May 11, 2015)
The US Supreme Court ruled on June 28, 2010 in McDonald v. Chicago that the Fourteenth Amendment, specifically the Due Process Clause, includes the Second Amendment right to keep and bear arms and, thus, the Second Amendment applies to the states as well as the federal government, effectively extending the individual rights interpretation of the Second Amendment to the states. 
On June 27, 2016, in Voisine v. United States, the Supreme Court ruled (6-2) that someone convicted of "recklessly" committing a violent domestic assault can be disqualified from owning a gun under the 1996 Lautenberg Amendment to the 1968 Gun Control Act. Associate Justice Elena Kagan, JD, writing the majority opinion, stated: "Congress enacted §922(g)(9) [the Lautenberg Amendment] in 1996 to bar those domestic abusers convicted of garden-variety assault or battery misdemeanors--just like those convicted of felonies--from owning guns."    
On Feb. 20, 2018, the US Supreme Court indicated it would not hear an appeal to California's 10-day waiting period for gun buyers, thus leaving the waiting period in place.  Justice Clarence Thomas said the Court should have heard the challenge, stating "The right to keep and bear arms is apparently this Court's constitutional orphan," in reference to the Court not hearing a major Second Amendment case since 2010. 
The National Rifle Association (NRA)
The National Rifle Association calls itself "America's longest-standing civil rights organization."  Granted charter on Nov. 17, 1871 in New York, Civil War Union veterans Colonel William C. Church and General George Wingate founded the NRA to "promote and encourage rifle shooting on a scientific basis" to improve the marksmanship of Union troops.  General Ambrose Burnside, governor of Rhode Island (1866 to 1869) and US Senator (Mar. 4, 1875 to Sep. 13, 1881), was the first president. 
Over 100 years later, in 1977, in what is known as the "Revolt at Cincinnati," new leadership changed the bylaws to make the protection of the Second Amendment right to bear arms the primary focus (ousting the focus on sportsmanship).  The group lobbied to disassemble the Gun Control Act of 1968 (the NRA alleged the Act gave power to the ATF that was abused), which they accomplished in 1986 with the Firearms Owners Protection Act. 
In 1993 the Centers for Disease Control (CDC) funded a study completed by Arthur Kellerman and colleagues, published in the New England Journal of Medicine, titled "Gun Ownership as a Risk Factor in the Home," which found that keeping a gun at home increased the risk of homicide.  The NRA accused the CDC of "promoting the idea that gun ownership was a disease that needed to be eradicated," and argued that government funding should not be available to politically motivated studies.  The NRA notched a victory when Congress passed the Dickey Amendment, which deducted $2.6 billion from the CDC's budget, the exact amount of its gun research program, and restricted CDC (and, later, NIH) gun research.  The amendment stated that "none of the funds made available for injury prevention and control at the Centers for Disease Control and Prevention may be used to advocate or promote gun control."  The admonition effectively stopped all federal gun research because, as Kellerman stated, "[p]recisely what was or was not permitted under the clause was unclear. But no federal employee was willing to risk his or her career or the agency's funding to find out."  Jay Dickey (R-AR), now retired from Congress, was the author of the Dickey Amendment and has since stated that he no longer supports the amendment: "I wish we had started the proper research and kept it going all this time... I have regrets." 
As of Jan. 2013, the NRA had approximately 3 million members, though estimates have varied from 2.6 million to 5 million members.  In 2013 the NRA spending budget was $290.6 million.  The NRA-ILA actively lobbies against universal checks and registration, "large" magazine and "assault weapons" bans, requiring smart gun features, ballistic fingerprinting, firearm traces, and prohibiting people on the terrorist watchlist from owning guns; and in favor of self-defense (stand your ground) laws.  In 2014 the NRA and NRA-ILA spent $3.36 million on lobbying activity aimed primarily at Congress but also the US Fish and Wildlife Service, National Park Service, Bureau of Land Management, Army Corps of Engineers, and the Forest Service. 
The Gun Control Lobby
The start of the modern gun control movement is largely attributed to Mark Borinsky, PhD, who founded the National Center to Control Handguns (NCCH) in 1974.  After being the victim of an armed robbery, Borinsky looked for a gun control group to join but found none, founded NCCH, and worked to grow the organization with Edward O. Welles, a retired CIA officer, and N.T. "Pete" Shields, a Du Pont executive whose son was shot and killed in 1975. 
Gun control activists, including Mayor Vincent Gray, march in Washington, DC Source: Bijon Stanard, "Let's Talk: Obama Speaks; Dr. King's March on Washington 50th Anniversary!," letstalkbluntly.com, Aug. 8, 2013
In 2001, after a few name changes, the National Center to Control Handguns (NCCH) was renamed the Brady Campaign to Prevent Gun Violence and its sister organization, the Center to Prevent Handgun Violence, was renamed the Brady Center to Prevent Handgun Violence, though they are often referred to collectively as the Brady Campaign.  The groups were named for Jim Brady, a press secretary to President Ronald Reagan who was shot and permanently disabled on Mar. 30, 1981 during an assassination attempt on the President. 
The 2014 gun control lobby was composed of Everytown for Gun Safety, Brady Campaign to Prevent Gun Violence, Coalition to Stop Gun Violence, Sandy Hook Promise, Americans for Responsible Solutions, and Violence Policy Center.  Collectively, these groups spent $1.94 million in 2014, primarily aimed at Congress but also the Executive Office of the President, the Vice President, the White House, Department of Justice, and the Bureau of Alcohol, Tobacco, and Firearms. 
The most-recently available total annual spending budgets for gun control groups were $13.7 million collectively (4.7% of the NRA's 2013 budget): including Everytown for Gun Safety ($4.7 million in 2012); the Brady Campaign ($2.7 million in 2012); the Brady Center ($3.1 million in 2010); Coalition to Stop Gun Violence ($308,761 in 2011); Sandy Hook Promise ($2.2 million in 2013); and the Violence Policy Center ($750,311 in 2012). 
The Current Gun Control Debate
Largely, the current public gun control debate in the United States occurs after a major mass shooting. There were at least 126 mass shootings between Jan. 2000 and July 2014.  Proponents of more gun control often want more laws to try to prevent the mass shootings and call for smart gun laws, background checks, and more protections against the mentally ill buying guns. Opponents of more gun laws accuse proponents of using a tragedy to further a lost cause, stating that more laws would not have prevented the shootings. A Dec. 10, 2014 Pew Research Center survey found 52% of Americans believe the right to own guns should be protected while 46% believe gun ownership should be controlled, a switch from 1993 when 34% wanted gun rights protected and 57% wanted gun ownership controlled.  According to a Feb. 20, 2018 Quinnipiac Poll taken shortly after the Feb. 14 mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, 66% of American voters support stricter gun control laws. 
On Dec. 18, 2018, the US Justice Department announced a new rule banning bump stocks, a gun attachment that allows a semi-automatic gun to fire rapidly like an automatic weapon. As of Mar. 26, 2019, the new rule classifies bump stocks as machine guns, which bans them nationwide under existing gun control laws.