In June 2016, 29-year-old Omar Mateen walked into Orlando's gay nightclub Pulse, and shot and killed 49 people. 53 others were wounded. It was the deadliest mass shooting in American history.
Mateen was born in New York to Afghan parents and had been on the FBI's radar a couple of times, once for inflammatory comments then again regarding a possible connection to an American suicide bomber in Syria. Both cases were closed.
Credit: CBS News
The world mourns
Following the shooting the world showed support for Orlando and its victims, mass vigils taking place from Hong Kong to Paris. "I am Orlando," said one message in Los Angeles. Speculation that Mateen himself had been gay could not be proven.
Rowan County Clerk Kim Davis
The battle for gay rights in America has been raging since the mid-twentieth century and is clearly nowhere near over.
On September 3, 2015, Rowan County Clerk Kim Davis was thrown in jail on a contempt of court charge for refusing to issue marriage licenses to same-sex couples at the Rowan County Courthouse in Morehead, Kentucky. She claims the Supreme Court ruling conflicts with her Christian faith.
Five days later, U.S. District Judge David Bunning lifted the contempt order against Davis, saying he was satisfied that her deputies are fulfilling their obligation to grant licenses in her absence. Bunning warned, however, that there will be trouble if Davis tries to interfere with the issuance of those licenses in any way.
Credit: Timothy D. Easley/AP
Rowan County Clerk Kim Davis is set to be released September 8, 2015, just before she was to receive jailhouse visits from presidential candidates Mike Huckabee and Ted Cruz.
On June 26, 2015, the Supreme Court ruled 5-4 that it is unconstitutional for states to ban same-sex marriages. This decision marked a long fought victory for the LGBT community that included many milestones of disappointment and tragedy on the road to equal rights.
Credit: Joshua Roberts/Reuters
In 1948, Dr. Alfred C. Kinsey, an American biologist and sex researcher, published a book of his findings, called "Sexual Behavior in the Human Male." The "Kinsey Report," as it came to be known, concluded that sexuality exists on a scale and that homosexual behavior is not limited to those who identify as homosexuals.
Rather, Kinsey's research found that 37 percent of all males enjoy homosexual relations at one point or another in their lives. These findings shocked the psychologists and psychiatrists of the time, who long considered homosexuality a sociopathic personality disorder.
Cold War Investigation
At the beginning of the Cold War, the U.S. government conducted a secret investigation into the sexual orientation of its employees.
On December 15, 1950, the findings of that investigation were then circulated to all members of Congress in the form of a Senate Report, entitled "Employment of Homosexuals and Other Sex Perverts in Government."
The report stated that, "those who engage in overt acts of perversion lack the emotional stability of normal persons," and as such, "constitute security risks" to the nation. Accordingly, thousands of gay men and women were dismissed from their positions within the U.S. government and military over the next few years, in what would become known as "the lavender scare."
Credit: Joel Robine/AFP/Getty Images
On April 27, 1953, President Dwight Eisenhower signed into law Executive Order 10450, which banned populations that pose security risks to the nation from working for the federal government or any of its private contractors.
The "security risks" listed in that executive order included neurotics, alcoholics and homosexuals.
Credit: AFP/Getty Images
Daughters of Bilitis
On September 21, 1955, the Daughters of Bilitis formed in San Francisco, as America's first lesbian rights organization.
Its purpose is to host social events and push for social change through education. Chapters quickly spring up in other cities across the country as well.
This photo shows 1960s newsletters from the New York chapter of the Daughters of Bilitis.
Credit: National Museum of American History
On August 30, 1956, Evelyn Hooker presents at the American Psychological Association Convention in Chicago.
She conducted Rorschach and other psychological tests and groups of both homosexual and heterosexual men, and concluded that they do not differ significantly enough to consider homosexuality a clinical entity.
Her paper, "The Adjustment of the Male Overt Homosexual," is groundbreaking and helps to explode the notion that homosexuality is a mental illness.
Credit: American Psychological Association Archives
Early in the morning on June 28, 1969, police attempted to raid a Greenwich Village gay bar, called the Stonewall Inn.
The gay youth inside, however, were sick of police raiding their bars in attempt to rid local neighborhoods of "sexual deviants." So, they fought back.
Thousands of protestors clashed with police officers in the streets outside Stonewall for three days. The riots are credited with reigniting the modern gay rights movement in America, and the Stonewall Inn was granted landmark status in June 2015.
Credit: Diana Davies/New York Public Library
On June 28, 1970, the one-year anniversary of the Stonewall Riots, thousands of members of the LGBT community took to the streets of Manhattan and marched all the way to Central Park.
This "Christopher Street Liberation Day" is now considered America's first gay pride parade.
Credit: Leonard Fink
UpStairs Lounge arson attack
On June 24, 1973, the Upstairs Lounge -- a gay bar on the second floor of a building in the French Quarter of New Orleans -- was intentionally set on fire, and 32 people perished inside.
Most of the victims were found near the windows in the background, attempting to escape the blaze. This arson incident remains the deadliest attack on the LGBT community in United States history. And no one was ever charged with the crime.
Here, the charred remains of the Upstairs Lounge are seen on June 25, 1973, the day after the attack.
Credit: Jack Thornell/AP
One, Inc. v. Olesen
In January 1958, the Supreme Court took up the historic case, One, Inc. v. Olesen; a suit, which was filed after the U.S. Postal Service and the FBI declared the contents of "One: The Homosexual Magazine," obscene.
Citing the First Amendment, it was the first time the U.S. Supreme Court ruled in favor of gay rights.
Credit: Mladen Antonov/AFP/Getty Images
In January 1974, Kathy Kozachenko is elected to the Ann Arbor, Michigan City Council, becoming the first openly gay American ever elected to public office.
Then, on November 8, 1977, Harvey Milk, seen here, wins a seat on the San Francisco Board of Supervisors, becoming the first openly gay man to be elected to public office in California. Before his assassination in 1978, Milk used his political position to fight discrimination against members of the LGBT community in the workplace.
Credit: AP Photo
March on Washington - 1987
On October 11, 1987, after six years of federal inaction with regards to the rapidly worsening AIDS crisis, 50,000 gay rights activists marched on Washington to demand that President Reagan address the epidemic.
In this photo, terminally ill AIDS victims are pushed in wheelchairs as they participate in the National March on Washington for Lesbian and Gay Rights.
Credit: Scott Stewart/AP
Understanding Aids brochure
In May 1988, the federal government finally addresses the AIDS crisis by mailing a CDC brochure, entitled "Understanding AIDS," to every household in America
Credit: Centers for Disease Control
Don't Ask, Don't Tell
On December 21, 1993, the Defense Department issues a new policy, stating that applicants to the United States military, "shall not be asked or required to reveal whether they are homosexual."
This directive, "Don't Ask, Don't Tell," is a small step forward in prohibiting discrimination in the armed forces. It, however, still forbids servicemen and women from participating in homosexual acts and/or telling anyone they are homosexual.
Credit: Alex Wong/Getty Images
Defense of Marriage Act
On September 21, 1996, President Clinton signs the Defense of Marriage Act (DOMA) into law.
In doing so, he makes the legal definition of marriage, a union between one man and one woman. As such, states no longer have to recognize same-sex unions, which were officiated beyond their borders.
Credit: Luke Frazza/AFP/Getty Images
On October 7, 1998, a gay college student, named Matthew Shepard, was tortured and murdered near Laramie, Wyoming because of his sexual orientation.
In response, thousands of people converged outside the U.S. Capitol, demanding some sort of political action to help stop hate crimes and draw attention to victims of anti-gay violence.
Here, Senator Edward Kennedy (D-MA) gestures to the crowd as he walks to a podium at the U.S. Capitol to give a speech in Matthew Shepard's honor, a week after the young man's death.
Credit: Andrew Cutraro/AFP/Getty Images
Civil Unions - Vermont
On April 26, 2000, civil unions and registered partnerships between same-sex couples are legalized in Vermont.
Carolyn Conrad (R) and Kathleen Peterson sign their civil union license at a town clerks' office in Vermont, at midnight on July 1, 2000. They became the first couple to enter a legalized civil union in the United States.
Credit: Toby Talbot/AP
Gay marriage - Massachusetts
On May 18, 2004, Massachusetts becomes the first state to legalize gay marriage, after its state Supreme Judicial Court concludes that marriage is a constitutional right.
Here, a crowd applauds a gay couple as they emerge from City Hall after applying for a marriage license in the early hours of May 17, 2004 in Cambridge, Massachusetts.
Cambridge City Hall opened its doors before midnight that night to become the first city in Massachusetts to issue licenses for same sex marriages.
Credit: Michael Springer/Getty Images
LGBT Presidential Forum
On August 9, 2007, the Human Rights Campaign teamed up with the Logo cable channel to host the first ever American presidential forum, focusing specifically on LGBT issues.
All of that year's presidential candidates were invited to participate, but only the six Democratic candidates did.
Here, New York Senator and Democratic presidential hopeful Hillary Rodham Clinton (R) fields questions at the Visible Vote '08 Presidential Forum in Los Angeles, California. From left are: panelists Jonathan Capehart, Joe Solmonese, Melissa Ethridge, and moderator Margaret Carlson.
Credit: Robyn Beck/AFP/Getty Images
On November 4, 2008, California voters approve Proposition 8 on their ballots, rendering gay marriage illegal in California and sparking protests across the country.
Thousands of gay marriage supporters carry signs during a rally against the passing of Prop. 8 in San Francisco, November 15, 2008.
Credit: Justin Sullivan/Getty Images
The passing of Prop. 8 in California sparks the creation of the NOH8 Campaign, a charitable organization and form of photographic silent protest, in which celebrities and gay rights supporters take pictures with duct tape over their mouths to symbolize gay rights 'being silenced.'
Here, actress Emmy Rossum attends a march following the California Supreme Court's ruling to uphold Proposition 8 in West Hollywood, California, May 26, 2009.
Credit: Kevork Djansezian/Getty Images
Hate Crimes Prevention Act
President Obama applauds the sisters of James Byrd, Jr. and the parents of Matthew Shepard, during a reception in the East Room of the White House, October 28, 2009 on the day Obama signed the Matthew Shepard and James Byrd, Jr., Hate Crimes Prevention Act into law. The expands the existing 1969 U.S. Federal Hate Crime Law to include crimes motivated by a victim's actual or perceived gender, sexual orientation, gender identity or disability.
In 1998, when Matthew Shepard was a college student in Wyoming, he was murdered for being gay. Byrd, an African American man, was dragged behind a pickup truck to his death in Texas that same year.
Credit: Saul Loeb/AFP/Getty Images
U.S. Senate repeals DADT
Activists listen during a "Don't Ask, Don't Tell" rally, held by the Service members Legal Defense Network, on Capitol Hill, before the vote on the National Defense Authorization Bill on December 18, 2010.
The U.S. Senate voted 65-31 to pass a National Defense Authorization Bill, which includes the repeal of "Don't Ask, Don't Tell." In doing so, gay Americans can now serve openly in the U.S. military.
Credit: Alex Wong, Getty Images
New York Pride
A number of states followed Massachusetts' example, including New York on June 24, 2011.
Here, people wave flags during the 2011 NYC LGBT Pride March on the streets of Manhattan, just days after New York state legislators approved the bill legalizing same-sex marriage.
Credit: Jemal Countess/Getty Images
Supreme Court says "I do"
On June 26, 2015, the Supreme Court ruled 5-4 that the U.S. Constitution provides same-sex couples the right to marry; a historic victory in the fight for gay rights.
Specifically, the Justices concluded that the Constitution's guarantees of due process and equal protection under the law mean that states cannot ban same-sex marriages.
Gay rights supporters celebrate outside the Supreme Court in Washington, DC, after the historic ruling.
Credit: Jim Bourg/Reuters
At 8:39 a.m. on June 26, 2015, in response to the Supreme Court upholding gay marriage, President Obama tweeted:
"This ruling is a victory for friends, families, and organizers who fought tirelessly for years for marriage equality. #LoveWins"
An avatar depicting the White House in rainbow colors then appeared on the White House's Twitter feed.