Here is the statement and the list of Mayors who have signed so far.

As mayors of great American cities, we proudly stand together in support of the freedom of same-sex couples to marry. We personally know many gay and lesbian people living in our cities who are in committed, loving relationships, who are active participants in the civic life of our communities, and who deserve to be able to marry the person with whom they share their life.    

We are proud that at its 2009 annual meeting, the U.S. Conference of Mayors unanimously approved a resolution stating that: “The U.S. Conference of Mayors supports marriage equality for same-sex couples, and the recognition and extension of full equal rights to such unions, including family and medical leave, tax equity, and insurance and retirement benefits, and opposes the enshrinement of discrimination in the federal or state constitutions.”    

Our cities derive great strength from their diversity, and gay and lesbian families are a crucial part. Studies have shown what we know through our hands-on experience—that cities that celebrate and cultivate diversity are the places where creativity and ideas thrive. They are the places where today’s entrepreneurs are most likely to choose to build the businesses of tomorrow. Allowing same-sex couples the right to marry enhances our ability to build this kind of environment, which is good for all of us.       

We stand for the freedom to marry because it enhances the economic competitiveness of our communities, improves the lives of families that call our cities home, and is simply the right thing to do.  We look forward to working to build an America where all people can share in the love and commitment of marriage with the person with whom they share their life.

Michael Bloomberg - New York, NY (Chair)   
Thomas Menino - Boston, MA (Chair)
Annise Parker - Houston, Texas (Chair)    
Jerry Sanders - San Diego, CA (Chair)
Antonio Villaraigosa - Los Angeles, CA (Chair)    
Samuel Adams - Portland, OR
Tom Bates - Berkeley, CA    
William Bell - Durham, NC
David Berger - Lima, OH    
Richard Bloom - Santa Monica, CA
Cory Booker - Newark, NJ    
Bruce Botelho - Juneau, AK
Ardell Brede - Rochester, MN    
Christopher Cabaldon - W. Sacramento, CA
John Callahan - Bethlehem, PA    
Stephen Cassidy - San Leandro, CA
Craig Cates - Key West, FL    
Mark Chilton - Carrboro, NC
Joshua Cohen - Annapolis, MD    
Chris Coleman - St. Paul, MN
Dennis Coombs - Longmont, CO    
Joy Cooper - Hallandale Beach, FL
Frank Cownie - Des Moines, IA    
John Duran - West Hollywood, CA
Paul Dyster - Niagara Falls, NY    
Rahm Emanuel - Chicago, IL
Bill Finch - Bridgeport, CT    
Peter Fosselman - Kensington, MD
Bob Foster - Long Beach, CA    
Laura Friedman - Glendale, CA
Ava Frisinger - Issaquah, WA    
Marie Gilmore - Alameda, CA
Mike Gin, Redondo Beach, CA    
Vincent Gray - Washington, D.C.
George Heartwell - Grand Rapids, MI    
John Hieftje - Ann Arbor, MI
Bobby Hopewell - Kalamazoo, MI    
Sylvester James, Jr. - Kansas City, MO
Edward Kelly - Cleveland Heights, OH    
Mark Kleinschmidt - Chapel Hill, NC
Mark Kruzan - Bloomington, IN    
Don Lane - Santa Cruz, CA
Timothy Leavitt - Vancouver, WA    
Edwin Lee - San Francisco, CA
Lee Leffingwell - Austin, TX    
Craig Lowe - Gainesville, FL
David Lublin - Town of Chevy Chase, MD    
Karen Majewski - Hamtramck, MI
Jan Marx - San Luis Obispo, CA    
Mike McGinn - Seattle, WA
Alex Morse - Holyoke, MA    
Lori Moseley - Miramar, FL
Jeri Muoio - West Palm Beach, FL    
David Narkewicz - Northampton, MA
Don Ness - Duluth, MN    
Michael Nutter - Philadelphia, PA
Frank Ortis - Pembroke Pines, FL    
Kitty Piercy - Eugene, OR
Steve Pougnet - Palm Springs, CA    
Jean Quan - Oakland, CA
Thomas Richards - Rochester, NY    
Clarissa Rowe - Arlington, MA
Matthew Ryan - Binghampton, NY    
RT Rybak - Minneapolis, MN
Robert Sabonjian - Waukegan, IL    
Helene Schneider - Santa Barbara, CA
Ann Schwab - Chico, CA    
Pedro Segarra - Hartford, CT
Eric Senter - Franklinton, NC    
Jeffrey Slavin - Town of Somerset, MD
Paul Soglin - Madison, WI    
Marilyn Strickland - Tacoma, WA
Angel Taveras - Providence, RI    
Nick Tell - Manhattan Beach, CA
Elizabeth Tisdahl - Evanston, IL    
Setti Warren - Newton, MA
Bruce Williams - Takoma Park, MD    
Dana Williams - Park City Park, UT

Read more: http://www.towleroad.com/2012/01/mayorsstateent.html#ixzz1k0wmlJqU