The U.S. Supreme Court on Tuesday will hear arguments in a case challenging gay marriage bans in four states.

A 2013 Supreme Court ruling striking down the Defense of Marriage Act (DOMA), which led to the federal government recognizing the marriages of gay couples, opened the doors to a flood of lawsuits challenging bans throughout the nation. Most appellate courts cited the high court's DOMA ruling in siding with plaintiffs, quickly increasing the number of states where gay couples can marry to 37, plus the District of Columbia.

However, the Cincinnati-based Sixth Circuit Court of Appeals broke rank. After hearing arguments from cases challenging bans in Ohio, Michigan, Kentucky and Tennessee, the court last year overturned lower court rulings striking down bans in those states. Plaintiffs turned to the Supreme Court, which agreed to review the cases as one.

Arguments will be divided into two parts, with the first 90 minutes devoted to the constitutionality of state marriage bans, followed by an hour of debate on whether the U.S. Constitution requires states to recognize the out-of-state marriages of gay couples.

On the eve of the landmark hearing, activists from both sides converged on the Supreme Court Plaza.

Together 27 years, Frank Colasonti Jr. and James Ryder of Birmingham, Michigan told ABC News that they've been waiting in line for coveted chairs inside the court since Friday. The couple married last year.

“It really never seemed like an option that it would ever happen,” Ryder said.