Colorado’s civil unions law that takes effect on May 1 will have a midnight coming-out party in Denver’s Webb Building, where Mayor Michael Hancock will preside over some of the first ceremonies.

The event in the atrium of the Webb Building at 201 W. Colfax Ave. is being organized by One Colorado — a statewide lesbian, gay, bisexual, transgender advocacy group. Denver’s Office of the Clerk and Recorder is facilitating the event, opening the doors at 10:30 p.m. April 30 to welcome couples who wish to be among the first in Colorado to enter into a civil union.

From midnight to 2 a.m., One Colorado will offer civil union ceremonies to couples, which will be performed by local judges, magistrates, and qualified religious and lay officiants.

The Clerk and Recorder’s Office will pick up the tab for opening up the building and paying for security services, four police officers and staff employees to work the event, said Nancy Reubert, clerk’s spokeswoman.

“The party in the atrium is (One Colorado’s). Everything that goes on in the atrium is their deal,” she said. “We are the city agency who is hosting them and opening up the building and making sure it is secure. … We don’t think this is going to be a giant expense.”

Hancock said he is “honored to take part in this historic event, uniting committed couples who were for too long excluded from the same benefits and protections provided to their fellow citizens. At midnight May 1, our great state will bring down some of the senseless walls that have divided us and state in one voice: ‘Everyone matters.’ “

Jeremy P. Meyer: 303-954-1367, jpmeyer@denverpost.com or twitter.com/jpmeyerdpost