Minnesota's major companies and law firms have some of the nation's most gay-friendly policies, a leading gay advocacy group reports.

Their average score, 90 out of 100, is topped by firms in just three states, two in New England and neighboring Iowa, a heartland pioneer when it came to same-sex marriage.

"Nationally Minnesota is very much a bastion of leadership in this area," said Deena Fidas, director of the workplace program for the Washington, D.C.-based Human Rights Campaign.

"When you have 3M, Ameriprise, with perfect scores, as well as household names like Best Buy, Hormel, General Mills," she said, "it really is incredible to see that."

The advocacy group prefers not to rank states, for a variety of reasons. But it agreed to release internal data on hundreds of firms across the nation to the Star Tribune to carry out its own computer analysis.

Of 28 Minnesota firms evaluated, 15 scored a perfect 100, including high-profile names such as Target Corp., controversially a contributor in 2010 to a right-wing gubernatorial candidate opposing gay rights.

General Mills, by contrast, is mentioned repeatedly by activists as a brave rarity in declaring its 2012 opposition to a proposed constitutional amendment seeking to outlaw gay marriage. Both firms were loudly criticized for taking political stances that threatened to alienate customers.

Monica Meyer, executive director of OutFront Minnesota, an LGBT rights group, said the rankings serve an important purpose in defining precisely what constitutes an inclusive workplace.

"A lot of times you hear them say, 'We didn't even know we should be doing this!' " she said.

The group asks firms whether they have LGBT nondiscrimination policies, whether they extend benefits to same-sex partners, what their policies are on transgender employees, and whether they publicly commit to LGBT equality, among other things.

Only five of the Minnesota firms score below 85, although they do include a pair of high-profile entities: Mayo Clinic (65) and Caribou Coffee (50).

Sharonne Hayes, director of Mayo's Office of Diversity and Inclusion, said in an e-mail that Mayo's score was "surprising" and "a marked departure from previous years, and does not align with preliminary scores we were shown."

She said Mayo was "not given the opportunity" to discuss the score with the Human Rights Campaign to "clear up any confusion …

"In short, Mayo Clinic has in place policies and benefits that promote equality and inclusion among all employees, contractors, and patients who identify as LGBTI," she said.

Caribou Coffee did not respond to an e-mail inquiry about its score.

Of the three states outranking Minnesota nationally, only one, Connecticut, has an appreciable number of firms large enough to fall under the spotlight. Vermont has just two, including Ben & Jerry's ice cream, while Iowa has four, none scoring lower than 90.

States tied with Minnesota, with an average score of 90, were Illinois, New York, Missouri and Washington state. Southern states tended to rank toward the bottom of the list. Arkansas, for instance, had no firms with perfect scores, though Wal-Mart did register a 90.

David Peterson • 651-925-5039