Same-sex couples in Washington, D.C., can head to city hall Wednesday to apply for marriage licences, as the federal district becomes the most recent place in the United States to approve gay marriage.

Some city officials were expecting as many as 200 people to descend on city hall Wednesday in search of marriage licences. Rick Imirowicz, who hopes to marry his partner Terrance Heath, said he plans on being one of them.

"There’s all kinds of benefits that come with marriage of course, protections that come with it,” Imirowicz said.

Imirowicz and Heath have been together for 10 years and are raising two adopted children.

“It’s terribly exciting,” Heath said. “It means that our commitment is recognized and respected.”

New rules at marriage bureau

To prepare for Wednesday, the marriage bureau has changed its licence applications so they are gender-neutral, asking for the name of each "spouse" rather than the "bride" and "groom."

The booklet outlining how civil marriage ceremonies should be performed has also been changed. The instructions now read: "I now pronounce you legally married" instead of "I now pronounce you man and wife."

Because of a mandatory waiting period, same-sex couples won’t actually be able to get married in the District of Columbia until March 9.

The decision to approve gay marriage, however, means the nation’s capital is joining Connecticut, Iowa, Massachusetts, New Hampshire and Vermont — the only states in the U.S. that issue same-sex marriage licences.

Supreme Court refuses to block bill

The gay marriage law was introduced in the 13-member D.C. Council in October and had near-unanimous support from the beginning.

The bill passed and D.C. Mayor Adrian M. Fenty signed it in December. On Tuesday, the U.S. Supreme Court refused to block the district's gay marriage law.

"It has been the practice of the court to defer to the decisions of the courts of the District of Columbia on matters of exclusively local concern," said Chief Justice John Roberts, writing for the court.

He also pointed out that Congress, which had a chance to review the law because Washington is a federal district, could have voted to stop the city government from putting the law into effect.

Opponents, however, are still attempting to overturn the bill in court.

For Heath, news that opponents will try to fight the new rules isn't surprising.

“There are always setbacks and advances when you’re moving toward fairness and equality for everyone,” he said.

with files from CBC News