This year marks the 30th anniversary of the passage of a law making March Women’s History Month in the United States.

The observation, which was born out of a California school district’s celebration of women’s achievements, now is celebrated across the country, and includes parades, lectures, health screenings, art exhibits and other activities that highlight women’s contributions to society.

Here’s a look at the history of the movement, why it’s celebrated in March, this year’s theme and the National Women’s History Project honorees.

What is it?

Women's History Month is a celebration of women's contributions to society.

When is it?

In the United States, it is celebrated each year in March.

Why March?

March was chosen as the month to celebrate women’s history because the first observances of Women’s History Week revolved around International Women’s Day, which is March 8. International Women’s Day, which honors women’s achievements worldwide, was first celebrated on March 8, 1911. The United Nations has sponsored International Women’s Day observances since 1975.

How did it start?

In 1978, a school district in Sonoma, California, decided to honor women's achievements by participating in a Women's History Week event. According to the National Women's History Project, schools hosted essay contests, presentations by women were given at many of the schools in the district and a parade was held in downtown Santa Rosa, California.

The following year, a two-week conference examining women’s history was held at Sarah Lawrence College. Those participating in the conference learned about Sonoma County's Women's History Week celebration and decided to organize similar celebrations within their own schools and organizations.

During the following seven months, they lobbied for a declaration of Women’s History Week and in March 1980, President Jimmy Carter issued a presidential proclamation declaring the week of March 8, 1980, as National Women's History Week.

In 1981, Sen. Orrin Hatch, R-Utah, and Rep. Barbara Mikulski, D-Md., co-sponsored a joint congressional resolution calling the week of March 7, 1982, Women's History Week.

Schools across the country began to incorporate Women’s History Week into their curriculum and, eventually, the week grew into a monthlong observance.

Fourteen states had declared March Women’s History Month by 1986. In 1987, the National Women’s History Project asked Congress to establish March as Women’s History Month. On March 12, 1987, the celebration became official when legislation was passed to designate March as Woman’s History Month in the United States.

What is this year’s theme?

The 2018 National Women’s History Month theme is “Nevertheless, She Persisted: Honoring Women Who Fight All Forms of Discrimination against Women.”

The theme refers to remarks made by Senate Majority Leader Mitch McConnell, R-Ky., after he objected to Sen. Elizabeth Warren, D-Mass., reading a letter from civil rights leader Coretta Scott King that condemned then-Sen. Jeff Sessions, R-Ala. The Senate was debating Sessions nomination to become U.S. attorney general. McConnell objected to the reading of the letter on the grounds of “Rule XIX” which prohibits ascribing "to another senator or to other senators any conduct or motive unworthy or unbecoming a senator.” He called for a vote to silence Warren, which passed on party lines.

Who is being honored this year?

Here, from the National Women’s History Project, is a list of those being honored this year.

  1. Susan Burton: Burton founded A New Way of Life Re-Entry Project in 1998 to help women break the cycle of incarceration. Burton is a co-founder of All of Us or None and the Formerly Incarcerated and Convicted People's Movement, both national grassroots civil rights movements comprised of formerly incarcerated individuals, their families and community allies.
  2. Margaret Dunkle: Dunkle played a key role in implementing Title IX, the law that transformed education for women and girls, from athletic fields to graduate schools. Her groundbreaking 1974 report documenting discrimination against female athletes became the blueprint for the Title IX regulations on athletics. Dunkle crafted the 1986 legislation that enabled low-income women to receive student aid without losing health insurance for their children.
  3. Geraldine Ferraro: Ferraro was the first female vice presidential candidate representing a major political party. In 1993 President Clinton appointed Ferraro U.S. ambassador to the United Nations on human rights, and in 1995 appointed her vice chair of the U.S. delegation to the Fourth World Conference on Women in Beijing.
  4. Jill Moss Greenberg: Greenberg is a lifelong crusader for fairness and the rights of underrepresented groups. She served as the first National Executive Director of NAME (the National Association for Multicultural Education).
  5. Roma Guy: Guy is a social justice activist and policy leader on homelessness, public health, poverty, LGBTQI rights, immigrant rights, and women's rights. She was a consultant and one of the LGBTQI activists featured in the 2017 ABC miniseries "When We Rise."
  6. Cristina Jiménez: Jimenez is a leader in the youth-led immigrant rights movement, and instrumental in creating the DACA program. She is executive director and co-founder of United We Dream, the largest immigrant youth-led organization in the country.
  7. Saru Jayaraman: Jayaraman responded to the 9/11 tragedy by organizing displaced World Trade Center workers and co-founding Restaurant Opportunities Centers United. ROC United is a leader in the "One Fair Wage" campaign to end the two-tiered minimum wage system.
  8. Marty Langelan: Langelan is a leader in the global effort to end harassment and gender-based violence. Langelan provides violence-intervention skills training for international human-rights organizations, anti-rape activists, environmentalists and others.
  9. Pat Maginnis: Maginnis is an abortion rights activist. In 1962 Maginnis founded the Society for Humane Abortion where she advocated for "elective abortion" and argued that all women had the right to safe and legal abortion. In 1966, she founded the Association to Repeal Abortion Laws.
  10. Arlene B. Mayerson: Mayerson is a leading attorney in disability rights law. She played a key role in drafting and negotiating the Americans with Disabilities Act and amendments to the Individuals with Disabilities Education Act.
  11. Pauli Murray: Murray was a civil rights and women's rights activist. She finished first in her class at Howard Law School where she was the only female student. She was denied admission to graduate school in 1938 due to her race and denied a fellowship to Harvard Law in 1944 due to her sex. She went on to be the first African-American awarded a law doctorate from Yale (1965) and later became the first African-American woman to be ordained an Episcopal priest (1977). President John F. Kennedy appointed her to the Presidential Commission on the Status of Women (1961) and she was a co-founder of the National Organization for Women in 1966.
  12. Elizabeth Peratrovich: Peratrovich, an Alaska native of the Tlingit Nation, was a civil rights leader. She petitioned Alaska officials to end segregation of native peoples. She was instrumental in the Feb. 16, 1945, anti-discrimination act to protect the civil rights of Alaska natives.
  13. Loretta Ross: Ross has dedicated her career to feminist issues with a focus on women of color. She helped create the theory of reproductive justice, adding a human rights framework to include everyone in reproductive rights issues. She is a visiting professor teaching courses on white supremacy, reproductive justice, and calling in practices at Hampshire College for the 2017-2018 academic year.
  14. Angelia Salas: Salas is a key strategist and leader in the national movement for immigrant rights and policy reform. She is the executive director of the Center for Humane Immigrant Rights.
  15. Linda Spoonster Schwartz: Schwartz overcame a military injury to become one of the nation's leading veterans' advocates, focusing especially on the unmet needs of women veterans. She was chair of the Department of Veterans Affairs' Advisory Committee on Women Veterans, served as Connecticut commissioner/commandant of veterans affairs, was nominated by President Barack Obama to be assistant secretary of veteran affairs for policy and planning. She is the first and only woman elected president of the National Association of State Directors of Veterans Affairs.