Nearly 300 U.S. mayors have pledged to support the legalization of gay marriage.

As it marks its first anniversary, the group Mayors for the Freedom to Marry has added 211 members since it launched with 80 mayors last January.

Atlanta Mayor Kasim Reed, who recently joined the group, told The Huffington Post that he previously believed civil unions were good enough for gay and lesbian couples.

“For most of my political career I would have been ahead of my time in supporting gay and lesbian issues,” he said. “There's a difference between civil unions and the rights that come with marriage. For many years I didn't believe there was a difference.”

Reed said the group “helps to create a space in time and an environment where more and more people in more conservative parts of the United States can come, over time, to the conclusion that I did.”

Mayors for the Freedom to Marry is co-chaired by Mayors Michael Bloomberg of New York City, Thomas M. Menino of Boston, Annise Parker of Houston and Antonio Villaraigosa of Los Angeles.