(CNN) -- Here is some background information about lesbian, gay, bisexual and transgender milestones in the United States.
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 other support for homosexuals.
April 1952 - The American Psychiatric Association's diagnostic manual lists homosexuality as a sociopathic personality disturbance.
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 US 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 that began as a newsletter published by the activist group Personal Rights in Defense and Education (PRIDE).
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.
1976 - After undergoing gender reassignment surgery in 1975, ophthalmologist and professional tennis player Renee Richards is banned from competing in the women's US Open because of a "women-born-women" rule. Richards challenges the decision and in 1977, the New York Supreme Court rules in her favor. Richards competes in the 1977 US Open but is defeated in the first round by Virginia Wade.
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. In November 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.
1978 - Inspired by Milk to develop a symbol of pride and hope for the LGBT community, Gilbert Baker designs and stitches together the first rainbow flag.
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. Neighbors attempted to evict Dr. Joseph Sonnabend from the building because he was treating HIV-positive patients.
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."
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 - 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 and beaten 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 Shepard. Eventually, they each receive two life sentences for killing Shepard.
October 12, 1998 - 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.
June 2003 - The US Supreme Court strikes down the "homosexual conduct" law, which decriminalizes same-sex sexual conduct, with their opinion in Lawrence v. Texas. The decision also reverses Bowers v. Hardwick, a 1986 US Supreme Court ruling that upheld Georgia's sodomy law.
May 17, 2004 - The first legal same-sex marriage in the United States takes place 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.
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.
August 12, 2009 - 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 US president to publicly support the freedom for LGBT couples to marry.
September 4, 2012 - The Democratic Party becomes the first major US 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 the first Wisconsin woman to be elected to the US Senate.
June 26, 2013 - In United States v. Windsor, the US 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 lower court rulings to stand, and therefore 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 28, 2015 - The US Supreme Court hears oral arguments on the question of the freedom to marry in Kentucky, Tennessee, Ohio and Michigan. On June 26 the Supreme Court rules that states cannot ban same-sex marriage. The 5-4 ruling had Justice Anthony Kennedy writing for the majority. Each of the four conservative justices writes their own dissent.
July 27, 2015 - Boy Scouts of America President Robert Gates announces "the national executive board ratified a resolution removing the national restriction on openly gay leaders and employees."
May 17, 2016 - The Senate confirms Eric Fanning to be secretary of the Army, making him the first openly gay secretary of a US military branch. Fanning previously served as Defense Secretary Carter's chief of staff, and also served as undersecretary of the Air Force and deputy undersecretary of the Navy.
June 24, 2016 - President Barack Obama announces the designation of the first national monument to lesbian, gay, bisexual and transgender (LGBT) rights. The Stonewall National Monument will encompass Christopher Park, the Stonewall Inn and the surrounding streets and sidewalks that were the sites of the 1969 Stonewall uprising.
June 30, 2016 - Secretary of Defense Carter announces that the Pentagon is lifting the ban on transgender people serving openly in the US military.
August 5-21, 2016 - A record number of "out" athletes compete in the summer Olympic Games in Rio de Janeiro. The Human Rights Campaign estimates that there are at least 41 openly lesbian, gay and bisexual Olympians -- up from 23 that participated in London 2012.
November 9, 2016 - Kate Brown is sworn in as governor of Oregon, a day after she was officially elected to the office. Brown becomes the highest-ranking LGBT person elected to office in the United States. Brown took over the governorship in February 2016 (without an election), after Democrat John Kitzhaber resigned amidst a criminal investigation.
April 4, 2017 - The 7th Circuit Court of Appeals rules that the Civil Rights Act prohibits workplace discrimination against LGBT employees, after Kimberly Hively sues Ivy Tech Community College for violating Title VII of the act by denying her employment.
June 27, 2017 - District of Columbia residents can now choose a gender neutral option of their drivers license. DC residents become the first people in the United States to be able to choose X as their gender marker instead of male or female on driver's licenses and identification cards. Similar policies exist in Canada, India, Bangladesh, Australia, New Zealand and Nepal.
June 30, 2017 - The US Department of Defense announces a six-month delay in allowing transgendered individuals to enlist in the United States military. Defense Secretary Jim Mattis writes that they "will use this additional time to evaluate more carefully the impact of such accessions on readiness and lethality."
July 26, 2017 - President Donald Trump announces via Twitter that "After consultation with my Generals and military experts, please be advised that the United States Government will not accept or allow Transgender individuals to serve in any capacity in the US Military..."
October 4, 2017 - In a memo to all federal prosecutors, Attorney General Jeff Sessions says that a 1964 federal civil rights law does not protect transgender workers from employment discrimination and the department will take this new position in all "pending and future matters."
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