CHICAGO (CBS) — Gov. Pat Quinn and Cook County Clerk David Orr will be among those in attendance for a historic ceremony next month, in which 30 gay and lesbian couples will be joined in civil unions in Millennium Park.

The event is set for June 2, the day after civil unions officially become legal in Illinois. It is being organized by the Chicago Commission on Human Relations’ Advisory Council on LGBT issues.

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Participants in the ceremony will get their civil union licenses from the County Clerk’s office on June 1. The law requires couples to wait until the day after they obtain licenses before holding a civil union ceremony.

The ceremony will be held in Wrigley Square, near the corner of Randolph Drive and Michigan Avenue, Gay Chicago Magazine reported.

It is not expected to be the first civil union ceremony in the state. Many couples across Illinois have already vied for having the first ceremony just after midnight, the magazine reported.

Orr will officiate the ceremonies, as will Cook County Circuit Court Chief Judge Timothy Evans, and members of the Alliance of Illinois Judges, a gay and lesbian judges’ group. Among the officiators will be Circuit Court Judge Tom Chiola, who became the first openly gay judge elected in the county in 1994, the magazine reported.

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Quinn is not expected to officiate.

The participating couples have already been chosen. Some signed up for the Civil Unions Tracker on the web sites of Lambda Legal and Equality Illinois, while others were suggested by gay and lesbian groups around the state, the magazine reported.

The legislation allowing for civil unions in Illinois was signed into law by Gov. Quinn on Jan. 31, after being approved by both houses of the state General Assembly in December.

If the weather doesn’t cooperate, the ceremony will be moved to the Cultural Center on the other side of Michigan Avenue, Gay Chicago Magazine reported.

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