By MICHELLE R. SMITHNEWPORT, R.I. (AP) a¿¿ A proposal to build a visitors center on the grounds of The Breakers, the Gilded Age Vanderbilt family mansion and national historic landmark, is dividing Newport's preservationists, neighbors, and even some family members in a seaside city where tourism is its lifeblood. The Preservation Society of Newport County, the nonprofit group that owns the 70-room mansion, says the center is badly needed to serve The Breakers' 400,000 annual visitors. Many opponents agree something is needed, but they want it across the street in the parking lot or elsewhere, not on the 13-acre grounds of the property, which they say would be irreparably damaged. During the months since the $4.2 million plan was released, then rejected by the city's Historic District Commission, the disagreement has devolved into a bitter fight, with opponents who once considered themselves allies of the Preservation Society now accusing it of steamrolling or cutting people out when they disagree. The Preservation Society says it has explored the alternatives, and its plan is the only feasible one to protect the magnificent home built by railroad magnate Cornelius Vanderbilt II. "We have hired the best people, the brightest people. They're very sensitive to the issues. There is no steamroller. We believe we're doing the right thing," said Don Ross, chairman of the group's board. Both sides say they're fighting for the future. Opponents set up a "Save the Breakers" Facebook page in August. The Preservation Society set up a competing page the next day, also called "Save the Breakers." On Friday, the National Park Service weighed in, siding with critics and asking the Preservation Society to reconsider a plan it said could damage the national historic landmark. The Preservation Society will go before the city's zoning board on Monday to appeal, and says if it's again turned down, it will go to court. In the meantime, the plan has drawn some high-profile detractors, including designer Gloria Vanderbilt, who in a letter to the editor of Newport This Week last summer decried the possibility that visitors to the "magical kingdom" her grandfather built would be greeted by "plastic, shrink-wrapped sandwiches."