PORTLAND – Officials weren’t expecting crowds on Wednesday when the city’s domestic partnership registry went into effect.

The registry allows same-sex and unmarried heterosexual couples in Portland to obtain many of the same rights enjoyed by husbands and wives.

In the month since the City Council approved the domestic partnership ordinance, Portland officials have been working out the mechanics of the registry.

To be registered, both partners must fill out a form – in person, in the presence of a city clerk – about the status and duration of their relationship. Both partners also have to show proof of residency and pay a $20 filing fee.

Even though Portland, along with about a dozen other municipalities in Maine, already provides health benefits to domestic partners, this measure officially recognizes domestic partners as family.

More than 70 U.S. communities, including Phoenix, Los Angeles, and Boston, already have some form of domestic partner registry giving domestic partners such rights as visitation at public health facilities, access to children and their records at public schools, and eligibility for programs and benefits offered to married couples.

The Portland plan will bestow many of those same rights.

Maine companies or institutions that already offer health benefits to both gay and unmarried heterosexual couples include L.L. Bean, Maine Medical Center, Bates College and Bowdoin College.

Jonathan Lee, executive director of the Maine Speakout Project, called the registry a “meaningful step toward recognizing that [gays and lesbians], too, have families.”

He also said he did not expect many couples to register the first day.

“This will filter out, and I’m sure there’ll be people coming forward and registering their relationship eventually,” he said.