Civil rights activists are paying close attention to the happenings in Washington, D.C., because today marks the first day the Supreme Court will hear one of the most divisive issues affecting the country—marriage equality.

Staying true to the timeline it announced in January, the country's high court will hear oral arguments in the two cases before it today and tomorrow. Today, the justices will hear Hollingsworth v. Perry, a case involving California's Proposition 8, which passed in 2008 and bars gay marriage in the state. The justices will decide on the constitutionality of that law.

Tomorrow, the court will hear U.S. v. Windsor, a case out of New York that challenges the Defense of Marriage Act (DOMA), which President Bill Clinton signed into law in 1996. DOMA bars federal recognition of same-sex marriages and prevents those couples from receiving the same federal benefits that heterosexual individuals do. Clinton has since switched sides on the issue—recently urging the Supreme Court to overturn DOMA.

The justices are expected to rule on both cases by the end of June.

The court will hear these cases at a time when marriage equality has more support than ever. Last year, President Barack Obama came out in support of gay marriage—the first sitting president ever to do so. According to a report on NPR today, support for gay marriage in America is 58 percent—up from only 44 percent four years ago. And in recent years, nine states and Washington, D.C., have all legalized gay marriage.

The legal path to marriage equality is more than 40 years in the making. Check out Reuters' timeline of gay marriage in the U.S.

Read more InsideCounsel stories about marriage equality and other LGBT issues: