 Gay couples have been celebrating their new rights |
Registered same-sex couples in New Jersey now have adoption and custody rights, as well as new allowances on hospital visits and medical rights.
It is the third state to allow civil unions, a step below the full marriage rights permitted in Massachusetts.
Gay rights activists vowed to press for "full marriage rights" in the US.
The US federal government and 45 states do not recognise the unions.
New Jersey joins Vermont and Connecticut in offering civil unions, while California offers broadly similar rights under the title of domestic partnerships.
Massachusetts is the only state to allow same-sex marriages with the same legal rights as heterosexual unions.
'Bittersweet'
Partners Thomas Mannix and Kevin Pilla, who have been together since 1983, were among the first couples to arrive at Asbury Park City Hall to apply for a civil union.
Mr Mannix, 44, said: "The things being granted are long overdue and very important to have, so we wanted to take advantage of it as soon as it was available.
"But it was also bittersweet because it's not full marriage. Once a separate class is made, a separate category, we get back to 'separate but equal,' which we've learned from the past doesn't work."
Ed Barocas, legal director of the American Civil Liberties Union's New Jersey chapter, suggested that the separate system of rights would not have been accepted had it been based on race.
Legislators in New Jersey created civil unions in December, less than two months after a state Supreme Court decision held that gay couples had a right to the same benefits as married couples.
Some social conservative groups, meanwhile, are pledging to block same-sex marriage by pressing for an amendment to the state constitution that prohibits such unions.
