Nearly 5,000 gay and lesbian couples entered a civil union in the year since Illinois legalized the union.

The law, signed by Democratic Governor Pat Quinn, went into effect on June 1, 2011.

The largest number of licenses issued were from Cook County, where 2,504 couples tied the knot. DuPage County came in second with 264 licenses issued, the BurrRidge Patch reported.

The anniversary comes as activists launch a new push for equal marriage rights for gay couples.

While a bill which would legalize marriage equality in Illinois has languished in the Illinois General Assembly, advocates this week filed two legal challenges to the state's ban.

The ACLU of Illinois and Lambda Legal are representing more than two dozen gay and lesbian couples who wish to marry in Illinois but are unable because state law defines marriage as a heterosexual union.

The legal challenges are supported by Illinois Attorney General Lisa Madigan.

The suits claim that Cook County Clerk David Orr's refusal to issue marriage licenses to gay couples violates their rights to due process and equal protection under the Illinois Constitution.

Orr released a statement in support of marriage equality: “The time is long past due for the state of Illinois to allow county clerks to issue marriage license to couples who want to make their commitment. I hope these lawsuits are the last hurdle to achieving equal marriage rights for all.”

(Related: Illinois Gov. Pat Quinn endorses gay marriage.)