CHICAGO — Long lines are expected to form early today at the Cook County Clerk’s downtown office of vital records as couples from across Chicago gather to be part of a historic moment — the issuing of the state’s first civil-union licenses for both same-sex and heterosexual couples.

The doors will open at 7:30 a.m. and the clerk’s office will celebrate what it calls “the momentous occasion” by awarding a special gift package to the first couple to get a license. Adding to the festive atmosphere, about 20 local businesses will be supplying gifts that will be raffled off to other couples in line.

As with marriage licenses, couples will have to pay a $35 fee and wait one day before they can hold a civil union ceremony. Couples who are already registered as domestic partners in Cook County but want to enter into a civil union will get a $20 discount and their domestic partnership will be automatically dissolved.

Those seeking civil union licenses in neighboring suburban counties should not expect the same pomp that will be found at the Daley Center.

“Our taxpayers probably wouldn’t appreciate us giving away gifts, especially in light of (today) being the last day for people to pay their first installment of their property taxes,” said DuPage County chief deputy clerk Paul Hinds.

Instead, officials will roll out ropes to help form orderly lines outside the county building, keep a couple of extra security staff on hand and set aside a grassy space outside for possible protesters — or well-wishers.

The 12 DuPage County staff members who issue marriage licenses will help to process the anticipated influx of civil union applications, Hinds said.

He expects that staffers will process about 36 applications an hour. “It’s going to be a busy day around here,” Hinds said.

In Kane County, Clerk John “Jack” Cunningham said he doesn’t anticipate any problems today.

“It’s just another service we have in providing documents to people,” he said.

Officials in each county said they have not received an unusually large number of calls from people inquiring about the licenses, nor have they received any backlash from opponents of the new law.

Illinois will be the sixth state that allows civil unions or their equivalent, which provide couples with the same state-level rights as marriage. Two other states — Hawaii and Delaware — have passed civil union laws that have not yet been enacted.