(CNN) -- Read CNN's Fast Facts on Lesbian, Gay, Bisexual and Transgender Milestones in the United States, and learn more about the struggle for LGBT equal rights.
Timeline: 1924 - The Society for Human Rights is founded by Henry Gerber in Chicago. It is the first documented gay rights organization.
1950 - The Mattachine Society is formed by activist Harry Hay and is one of the first sustained gay rights groups in the United States. The Society focuses on social acceptance and support for homosexuals.
April 1952 - Homosexuality is listed as a sociopathic personality disturbance in the American Psychiatric Association's diagnostic manual.
April 27, 1953 - President Dwight D. Eisenhower signs an Executive Order that bans homosexuals from working for the federal government, saying they are a security risk.
September 1955 - The first known lesbian rights organization in the United States forms in San Francisco. Daughters of Bilitis (DOB). They host private social functions, fearing police raids, threats of violence and discrimination in bars and clubs.
July 1961 - Illinois becomes the first state to decriminalize homosexuality by repealing their sodomy laws.
September 11, 1961 - The first U.S. televised documentary about homosexuality airs on a local station in California.
June 28, 1969 - Police raid the Stonewall Inn in New York City. Protests and demonstrations begin, and it later becomes known as the impetus for the gay civil rights movement in the United States.
1969 - The "Los Angeles Advocate," founded in 1967, is renamed "The Advocate." It is considered the oldest continuing LGBT publication and began as a newsletter published by the activist group Personal Rights in Defense and Education (PRIDE).
1970s - The Pink Triangle becomes a symbol of gay pride after being used during World War II as a symbol of homosexuality, perversion and deviance.
June 28, 1970 - Community members in New York City march through the local streets to recognize the one-year anniversary of the Stonewall riots. This event is named Christopher Street Liberation Day, and is now considered the first gay pride parade.
1973 - Lambda Legal becomes the first legal organization established to fight for the equal rights of gays and lesbians. Lambda also becomes their own first client after being denied non-profit status, the New York Supreme Court eventually rules that Lambda Legal can exist as a non-profit.
January 1, 1973 - Maryland becomes the first state to statutorily ban same-sex marriage.
March 26, 1973 - First meeting of "Parents and Friends of Gays," which goes national as Parents, Families and Friends of Lesbians and Gays (PFLAG) in 1982.
December 15, 1973 - By a vote of 5,854 to 3,810, the American Psychiatric Association removes homosexuality from its list of mental disorders in the DSM-II Diagnostic and Statistical Manual of Mental Disorders.
1974 - Kathy Kozachenko becomes the first openly LGBT American elected to any public office when she wins a seat on the Ann Arbor, Michigan City Council.
1974 - Elaine Noble is the first openly gay candidate elected to a state office when she is elected to the Massachusetts State legislature.
January 14, 1975 - The first federal gay rights bill is introduced to address discrimination based on sexual orientation. The bill later goes to the Judiciary Committee but is never brought for consideration.
March 1975 - Technical Sergeant Leonard P. Matlovich reveals his sexual orientation to his commanding officer and is forcibly discharged from the Air Force six months later. Matlovich is a Vietnam War veteran and was awarded both the Purple Heart and the Bronze Star. In 1980, the Court of Appeals rules that the dismissal was improper. Matlovich is awarded his back pay and a retroactive promotion. Upon his death, the inscription on his gravestone read: ''When I was in the military they gave me a medal for killing two men and a discharge for loving one.''
1976 - After undergoing gender reassignment surgery in 1975, opthalmologist and professional tennis player Renee Richards is banned from competing in the women's U.S. Open because of a "women-born-women" rule. Richards challenges the decision and in 1977, the New York state supreme court rules in her favor. Richards competes in the 1977 U.S. Open but is defeated in the first-round by Virginia Wade.
May 24, 1976 - "Tales of the City," by Armistead Maupin appears in the San Francisco Chronicle. It is among the first fiction works to address a disease that initially affected gay men (it would later be identified as AIDS), and feature many minority characters and homosexual relationships.
1977-1981 - Billy Crystal plays one of the first openly gay characters in a recurring role on a prime time television show in "Soap."
January 9, 1978 - Harvey Milk is inaugurated as San Francisco city supervisor, and is the first openly gay man to be elected to a political office in California.
1978 - Inspired by Harvey Milk to develop a symbol of pride and hope for the LGBT community, Gilbert Baker designs and stitches together the first rainbow flag.
November 27, 1978 - Harvey Milk and Mayor George Moscone are murdered by Dan White, who had recently resigned from his San Francisco board position and wanted Moscone to reappoint him. White later serves just over five years in prison for voluntary manslaughter.
October 14, 1979 - The first National March on Washington for Lesbian and Gay Rights takes place. It draws an estimated 75,000 to 125,000 individuals marching for LGBT rights.
March 2, 1982 - Wisconsin becomes the first state to outlaw discrimination based on sexual orientation.
1983 - Lambda Legal wins People v. West 12 Tenants Corp., the first HIV/AIDS discrimination lawsuit.
December 1, 1988 - The World Health Organization holds the first World AIDS Day in order to raise awareness.
November 30, 1993 - President Bill Clinton signs a military policy directive that prohibits openly gay and lesbian Americans from serving in the military, but also prohibits the harassment of "closeted" homosexuals. The policy is known as "Don't Ask, Don't Tell."
1994 - The movie "Philadelphia," depicting a closeted gay man dying of AIDS, wins two Academy Awards.
November 1995 - The Hate Crimes Sentencing Enhancement Act goes into effect as part of the Violent Crime Control and Law Enforcement Act of 1994. The law allows a judge to impose harsher sentences if there is evidence showing that a victim was selected because of the "actual or perceived race, color, religion, national origin, ethnicity, gender, disability, or sexual orientation of any person."
September 21, 1996 - President Bill Clinton signs the Defense of Marriage Act, banning federal recognition of same-sex marriage and defining marriage as "a legal union between one man and one woman as husband and wife."
December 3, 1996 - Hawaii's Judge Chang rules that the state does not have a legal right to deprive same-sex couples of the right to marry, making Hawaii the first state to recognize that gay and lesbian couples are entitled to the same privileges as heterosexual married couples.
April 1997 - Comedian Ellen DeGeneres comes out as a lesbian on the cover Time magazine, stating "Yep, I'm Gay."
April 30, 1997 - Ellen DeGeneres' character, Ellen Morgan on her self-titled TV series "Ellen," becomes the first leading character to come out on a prime time network television show.
April 1, 1998 - Martin Luther King, Jr.'s widow, Coretta Scott King asks the civil rights community to help in the effort to extinguish homophobia.
October 6-7, 1998 - Matthew Shepard is tied to a fence, beaten and left to die near Laramie, Wyoming. He is eventually found by a cyclist, who initially mistakes him for a scarecrow.
October 9, 1998 - Russell Henderson and Aaron McKinney from Laramie, Wyoming, make their first court appearance after being arrested for the attempted murder of Matthew Shepard. Eventually, they each receive two life sentences for killing Shepard.
October 12, 1998 - Matthew Shepard dies from his injuries sustained in the beating.
April 26, 2000 - Vermont being comes the first state to legalize civil-unions between same-sex couples.
May 17, 2004 - The first legal same-sex marriage in the United States occurs in Massachusetts.
September 6, 2005 - The California legislature becomes the first to pass a bill allowing marriage between same-sex couples. Governor Arnold Schwarzenegger vetoes the bill.
December 9, 2005 - "Brokeback Mountain" is released to limited audiences in New York, Los Angeles and San Francisco. The major motion picture, directed by Ang Lee, focuses on a love story between two men that stretches over decades, and survives in a time and place in which the two men's feelings for each other were utterly taboo. The film stars Jake Gyllenhaal and Heath Ledger, and goes on to win several Golden Globe Awards and Academy Awards.
October 25, 2006 - The New Jersey Supreme Court rules that state lawmakers must provide the rights and benefits of marriage to gay and lesbian couples.
May 15, 2008 - The California Supreme Court rules in re: Marriage Cases that limiting marriage to opposite-sex couples is unconstitutional.
November 4, 2008 - Voters approve Proposition 8 in California, which makes same-sex marriage illegal.
February 22, 2009 - Actor Sean Penn wins an Oscar for his role as Harvey Milk in the film, "Milk." The film also won for Best Original Screenplay.
August 12, 2009 - Harvey Milk is posthumously awarded the Medal of Freedom by President Barack Obama.
October 28, 2009 - President Barack Obama signs the Matthew Shepard and James Byrd, Jr. Hate Crimes Prevention Act into law.
August 4, 2010 - Proposition 8 is found unconstitutional by a federal judge.
September 20, 2011 - "Don't Ask, Don't Tell" is repealed, ending a ban on gay men and lesbians from serving openly in the military.
May 9, 2012 - In an ABC interview, Barack Obama becomes the first sitting U.S. president to publicly support the freedom for LGBT couples to marry.
September 4, 2012 - The Democratic Party becomes the first major U.S. political party in history to publicly support same-sex marriage on a national platform at the Democratic National Convention.
November 6, 2012 - Tammy Baldwin becomes the first openly gay politician, and first Wisconsin woman, elected to the U.S. Senate.
June 26, 2013 - In United States v. Windsor, the U.S. Supreme Court strikes down section 3 of the Defense of Marriage Act, ruling that legally married same-sex couples are entitled to federal benefits. The high court also dismisses a case involving California's proposition 8.
October 6, 2014 - The United States Supreme Court denies review in five different marriage cases, allowing for lower court rulings to stand and allowing same-sex couples to marry in Utah, Oklahoma, Virginia, Indiana and Wisconsin. The decision opens the door for the right to marry in Colorado, Kansas, North Carolina, South Carolina, West Virginia and Wyoming.
June 9, 2015 - Secretary of Defense Ash Carter announces that the Military Equal Opportunity policy has been adjusted to include gay and lesbian military members.
April 24, 2015 - In a televised interview with ABC's Diane Sawyer, U.S. Olympic gold medal winner Bruce Jenner says, "Yes, for all intents and purposes, I'm a woman." Jenner later reveals that she is now Caitlyn Jenner and will live as a woman.
April 28, 2015 - The U.S. Supreme Court hears oral arguments on the question of the freedom to marry in Kentucky, Tennessee, Ohio and Michigan. The Supreme Court's decision is expected in late June 2015, and may bring a national resolution on the issue of same-sex marriage.
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