The Supreme Court announced Friday that it will decide a historic question about whether the Constitution requires that same-sex couples be allowed to marry no matter where they live or whether states are free to limit wedlock to its traditional definition as a union only between a man and a woman.

The court accepted cases from Michigan, Ohio, Kentucky and Tennessee, where restrictions about same-sex marriage were upheld by an appeals court in Cincinnati two months ago. The high court will hold 2 1/2 hours of oral arguments in April and decide the issue by the time the current term ends in June.

The justices ordered that the parties to the cases address two questions in their legal briefs: whether the Constitution requires states to issue marriage licenses to same-sex couples, and whether states must recognize same-sex marriages performed in other states where they are legal.

Advocates have called same-sex marriage the modern era’s most pressing civil rights issue, and the court’s action could mark the culmination of an unprecedented upheaval in public opinion and the nation’s jurisprudence.

The country’s first same-sex marriage, the result of a Massachusetts court decision, took place less than 11 years ago. Now, more than 70 percent of Americans live in states where same-sex couples are allowed to marry, according to estimates.

The questions raised in the cases that the court will consider this spring were left open in 2013 when the justices last confronted the issue of same-sex marriage. A slim majority said at the time that a key portion of the federal Defense of Marriage Act — withholding recognition of same-sex marriages — was unconstitutional and in a separate case allowed same-sex marriages to resume in California.

Since then, courts across the nation — with the notable exception of the Cincinnati appeals court — have struck down a string of state prohibitions on same-sex marriage, many of them passed by voters in referendums. Many of those court decisions compared the prohibitions to the ones on interracial marriage that the Supreme Court struck down in 1967 in Loving v. Virginia.

When the Supreme Court declined to review a clutch of those decisions in October, same-sex marriage proliferated across the country.

Couples may now marry in 36 states and the District. Three in four same-sex couples live in a state where they are allowed to wed, according to estimates by the Williams Institute at the UCLA School of Law.

Public attitudes toward such unions have undergone a remarkable change as well. Polls show that a majority of Americans support same-sex marriage, which was not sanctioned anywhere in the country at the turn of this young century.

After the court’s announcement Friday afternoon, Attorney General Eric H. Holder Jr. said that the Obama administration will file a friend-of-the-court brief asking the justices “to make marriage equality a reality for all Americans.”

Those on both sides of the issue agreed that the time had come for the Supreme Court to step in and settle the issue.

“It is time for the 50 million Americans who stood for marriage in 30 states to have their day in court,” said Brian Brown, president of the National Organization for Marriage, which opposes same-sex marriage. He said his groups expects “an eventual victory for the democratic process, religious liberty and the cherished institution of marriage, which forms the very bedrock of our society.”

But others, including many conservatives, think the outcome is foreshadowed by the court’s action in 2013.

When the justices declined in October to review the string of victories same-sex marriage proponents had won, it meant the number of states required to allow gay marriages grew dramatically, offering the kind of cultural shift the court often likes to see before approving a fundamental change.

“We are thrilled the court will finally decide this issue,” said James Esseks, director of the ACLU Lesbian Gay Bisexual Transgender & HIV Project. “The country is ready for a national solution that treats lesbian and gay couples fairly.

The Michigan case involves the issuance of marriage licenses to same-sex couples. The cases from Tennessee and Ohio concern whether states must recognize same-sex marriages performed in other states where such unions are legal. And Kentucky offers cases that touch on both licensing and recognition.

The coming cases are built on the court’s 2013 decisions.

In the DOMA case, U.S. v. Windsor, the decision written by Justice Anthony M. Kennedy said the federal government could not refuse to recognize or provide benefits to people in same-sex marriages that were conducted in states where they were legal.

Dozens of lower-court judges nationwide have read Kennedy’s opinion — in which he was joined by Justices Ruth Bader Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan — to mean that state bans violate constitutional rights as well.

Withholding federal recognition of same-sex married couples, Kennedy wrote in Windsor, ­places them “in an unstable position of being in second-tier marriages” and “demeans the couple, whose moral and sexual choices the Constitution protects . . . and whose relationship the State has sought to dignify.”

Kennedy, who sides with conservatives on most issues, is the pivotal member of the court and has written all of its modern decisions protecting gay rights, including Lawrence v. Texas, which struck down sodomy laws that targeted gay men.

But in his Windsor decision, Kennedy also cited the principles of state autonomy, which states have made central in arguments defending laws and state constitutional amendments defining marriage as only between a man and a woman.

Ohio Attorney General Mike DeWine (R), for instance, said, “It has always been Ohio’s position this is an issue for the people to decide.”

But Kennedy’s opinion in Windsor did not rest just on federalism. He said the states that allowed same-sex marriages “conferred upon them a dignity and status of immense import.”

He said the history of DOMA was written to convey moral disapproval of homosexuality and “a stigma upon all who enter into same-sex marriages made lawful by the unquestioned authority of the states.”

Chief Justice John G. Roberts Jr. and Justices Antonin Scalia, Clarence Thomas and Samuel A. Alito Jr. dissented in that case.

Roberts wrote separately in Windsor to point out that the decision did not pass judgment on state bans.

“We may in the future have to resolve challenges to state marriage definitions affecting same-sex couples,” he wrote. “That issue, however, is not before us.”

But most lower-court judges thought the logic of the majority argument indicated that the bans were unconstitutional. And many of them cited Scalia’s caustic dissent in Windsor.

“It takes real cheek for today’s majority to assure us, as it is going out the door, that a constitutional requirement to give formal recognition to same-sex marriage is not at issue here,” Scalia wrote.

Instead, “the majority arms well every challenger to a state law restricting marriage to its traditional definition,” Scalia wrote, and such suits are a “second . . . shoe to be dropped later.”

But almost everyone was surprised by how quickly that shoe dropped. Within six months, the first federal judge had struck down a ban, in Utah. Quickly, judges nationwide, and panels of the U.S. Courts of Appeals for the 4th, 7th, 9th and 10th circuits, struck down state bans.

In October, the justices declined to review those decisions without giving any reason. But Ginsburg, who has performed several same-sex marriages since the Windsor decision, has said in interviews that there is no need for the high court to intervene when lower courts are in agreement.

That changed in November, when a panel of the U.S. Court of Appeals for the 6th Circuit in Cincinnati upheld the bans in Kentucky, Michigan, Ohio and Tennessee.

Circuit Judge Jeffrey S. Sutton, writing for himself and Judge Deborah L. Cook, rejected the Windsor analysis that led other appeals courts to strike down the bans on same-sex marriage.

In his decision, Sutton repeatedly returned to the principle of democratic action, saying advocates of same-sex marriage would be better off by persuading their fellow citizens than by asking federal judges to force the issue.

“When the courts do not let the people resolve new social issues like this one, they perpetuate the idea that the heroes in these change events are judges and lawyers,” Sutton wrote. “Better in this instance, we think, to allow change through the customary political processes, in which the people, gay and straight alike, become the heroes of their own stories by meeting each other not as adversaries in a court system but as fellow citizens seeking to resolve a new social issue in a fair-minded way.”

Senior Judge Martha Craig Daughtrey said in a sharply worded dissent, said federal judges are required to protect the constitutional rights of the minority.

“If we in the judiciary do not have the authority, and indeed the responsibility, to right fundamental wrongs left excused by a majority of the electorate, our whole intricate, constitutional system of checks and balances, as well as the oaths to which we swore, prove to be nothing but shams,” she wrote.

The cases accepted by the court are Obergefell v. Hodges (Ohio), Tanco v. Haslam (Tennessee), DeBoer v. Snyder (Michigan) and Bourke v. Beshear (Kentucky).