1976: In Planned Parenthood of Central Missouri v. Danforth, the Supreme Court declares a statute that requires parental and spousal consent for abortions unconstitutional.

Congress enacts the Hyde Amendment for the first time, banning the use of federal funds for abortion except in cases of rape, incest or endangerment of the mother's life. This amendment has been attached to the congressional appropriations bill and approved by Congress every year since then.

1983: In Akron v. Akron Center for Reproductive Health, the Supreme Court declares unconstitutional an Ohio law that requires all abortions after the first trimester be performed at a hospital, a 24-hour waiting period and parental consent for girls younger than 15.

1989: The Supreme Court deals a blow to anti-abortion forces in Webster v. Reproductive Health Services by striking down a law that requires doctors to test the viability of the fetus before an performing any abortion. Three justices said they would allow restrictions on abortion but only if the restrictions had a rational basis.

1992: Supporters on either side of the abortion issue are left confused after the Supreme Court rules on Planned Parenthood of Southeastern Pennsylvania. v. Casey. The court says abortion regulations that present an "undue burden" on women's constitutional right will be prohibited; critics say "undue burden" is too vague.

1994: President Bill Clinton signs the Abortion-Clinic Protection Bill into law, which is designed to protect abortion clinics from attacks, blockades and acts of intimidation by anti-abortion protesters.

2000: The Food and Drug Administration approves the abortion pill RU-486. The drug enables a woman to terminate a pregnancy within seven weeks from her last menstrual period, without the need for a surgical abortion.

2003: President George W. Bush signs the "partial-birth abortion" bill, outlawing the procedure known as intact dilation and extraction (D&X). Federal judges quickly issue injunctions that temporarily nullify the law's effect for many abortion providers.

2004: About 800,000 demonstrators gather in Washington for the "March for Women's Lives," a protest against Bush's reproductive rights policies. This is the largest abortion-rights demonstration since a 1992 rally that drew at least 500,000 participants.

2007: The Supreme Court upholds the partial-birth abortion law 5-4 in the first federal restriction on a particular abortion method since Roe v. Wade.

In a bitter dissent read from the bench, Justice Ruth Bader Ginsburg says the majority's opinion "cannot be understood as anything other than an effort to chip away a right declared again and again by this court."

2009: President Barack Obama ends a ban on the use of U.S. foreign aid funds by international family planning programs that provided abortions or advice on obtaining one. The ban had first been instituted in 1984 by President Ronald Reagan.

George Tiller, a physician who performed late-term abortions, is shot and killed in Wichita, Kansas. Tiller, who had been subject to anti-abortion protests and harassment for more than 20 years, was the first abortion provider killed since 1998.

2011: Voters in Mississippi reject the "personhood" amendment, which would have outlawed all forms of abortion, including for cases of rape, incest and life-threatening pregnancies.

Research from the Alan Guttmacher Institute finds the number of abortions is at its lowest level since Roe v. Wade, remaining steady at about 1.2 million reported procedures in 2011, down 25 percent since the all-time high in 1990.

2012: Susan G. Komen for the Cure announces it will cut off funding to affiliates of Planned Parenthood. The organization reverses the decision three days later amid a public outcry.

The Supreme Court upholds Obama's Affordable Care Act, better known as Obamacare. Starting in 2014, the level of abortion coverage each woman will receive will depend on their state's policy, according to the Kaiser Family Foundation.

The ACA prohibits states from including abortion in any essential benefits package and no plan in an insurance exchange is required to offer abortion coverage. In addition, states can bar all plans participating in the exchanges from covering abortions.

Sources: "When Abortion Was A Crime," by Leslie Reagan; Kaiser Family Foundation; 4,000 Years For Choice; NPR; National Right to Life.