LOS ANGELES - When America's newest Roman Catholic cathedral opens in California next month, it will contain religious treasures borrowed from the country's oldest, the Basilica of the Assumption in Baltimore.

To mark the opening of the $200 million Cathedral of Our Lady of the Angels on Sept. 2, a Maryland-based group is preparing an exhibit there to celebrate Baltimore's basilica, known as the mother church of American Catholicism, which is poised to undergo a $25 million restoration.

For religious leaders in Los Angeles, the Baltimore exhibit is an opportunity to christen the new cathedral with art and artifacts that convey a sense of history and help trace the growth of Catholicism in America.

But the exhibit has the potential to offer much more than a history lesson. For stewards of Baltimore's basilica, the yearlong display is part of a campaign to spread the word about the restoration planned for the country's first cathedral.

Just as important, say leaders of the Basilica of the Assumption Historic Trust, it is a chance to raise the profile of the basilica as a national architectural landmark. They think the cathedral, built between 1806 and 1821, could be a tourism magnet for Baltimore - the American equivalent of St. Peter's in Rome - and want to start drawing national attention to it.

The Los Angeles exhibit is one of the first steps in that effort. Representatives of the trust, a nonprofit group formed to promote and protect the basilica, have also taken the lead in forming a nationwide consortium, called Latrobe's America to celebrate the basilica's architect, Benjamin Henry Latrobe.

They have begun a Web site (www.baltimorebasilica.org) and are seeking to have the basilica declared a World Heritage site, a United Nations designation reserved for places deemed to have international cultural significance.

"To get this exposure on the West Coast is great for Baltimore and great for the basilica," Wayne Ruth, chairman of the trust, said of the exhibit. "If we do this right, people will come from all over the world to see it."

Called "North America's most beautiful church" by architectural historian Nicholas Pevsner, the cathedral was designated a basilica in 1937 by Pope Pius XI. That rare honor is bestowed by papal decree or ancient custom.

The new effort is designed to restore the building - which has been refurbished 14 times since 1850 - as much as possible to the appearance envisioned by Latrobe and John Carroll, America's first Catholic bishop, and to upgrade it for continued use in the 21st century.

The work is scheduled to begin in the spring and be completed by late 2005, in time for the building's bicentennial. Plans also call for the addition of a "pilgrimage center" and museum on the grounds for visitors from around the world.

$18 million raised

The trust has been raising money locally for several years and has $18 million of the $25 million needed.

To build national support for the project, trust representatives have begun traveling across the country to promote their plans.

Late last month in Los Angeles, Ruth and architect John Waite announced plans for the cathedral exhibit at the California Club, a gathering spot for prominent Los Angeles business people, and gave a 90-minute lecture about the restoration at the Getty Center, the hilltop arts complex run by the J. Paul Getty Trust. Then Ruth flew to New Jersey for a cocktail party with prospective donors.

The Baltimore group might have been able to raise all of the money it needs without a national campaign, but members say they wanted to reach outside Maryland for two reasons.

First, they don't want to be accused of using money needed by the Archdiocese of Baltimore for other causes, such as school maintenance. By going outside Maryland and raising money specifically for the basilica restoration - such as a $100,000 grant received from the Getty Trust - they aren't likely to be criticized for diverting funds from other local projects.

Second, trustees want to make it clear that Baltimore's basilica is a national landmark that deserves widespread attention and support - and, ideally, more visitors. They think an exhibit inside the nation's newest and largest cathedral, serving the largest archdiocese in the nation, will go a long way toward showing that restoring Baltimore's basilica is a project of national significance.

"It's a great opportunity for us," Ruth said. "Every Catholic bishop in the country is going to be in Los Angeles for the opening of the new cathedral, and Baltimore's basilica will be featured prominently. The exhibit will make the point that American Catholicism had its roots in Baltimore and that restoration of Baltimore's basilica is a project that every Catholic ought to support."

Situated in one of the cathedral's side chapels, the exhibit will contain such Baltimore artifacts as the original cathedra, or bishop's throne; an 1811 oil portrait of Bishop John Carroll by Rembrandt Peale; a crozier, or shepherd's staff, that signifies the bishop's authority; and a portrait of Cardinal James Gibbons that was donated to the basilica by Eunice and Sargent Shriver.

Baltimore is also sending two brass candlesticks given to Archbishop Ambrose Marechal when the cathedral was dedicated in 1821; pieces from the altar setting in 1846; and a 5-foot-tall angel figure that originally guarded the tabernacle.

For the Los Angeles exhibit, planners are training docents and developing a brochure that will discuss the two cathedrals and what they have in common. There will also be an audiovisual presentation of the basilica's history and a virtual tour depicting the basilica after its restoration.

Baltimore Cardinal William H. Keeler and Bishop Gordon D. Bennett, formerly of the Archdiocese of Los Angeles, will lead a delegation from Maryland for the dedication of the new cathedral.

A reception introducing the Baltimore exhibit will be held at Loyola Marymount University the day before.

Los Angeles Cardinal Roger M. Mahony said he is grateful that Baltimore's exhibit could be ready in time for the grand opening of the Los Angeles cathedral Sept. 2.

"We wanted to have something from the Vatican, but that will come later," Mahony said. "This is perfect. The timing is very providential."

Mahony said he is counting on the treasures from Baltimore to tell a rich story about the growth of American Catholicism.

'Strong link'

When Baltimore's cathedral was under construction nearly 200 years ago, "who would have thought there would even be a cathedral on the West Coast?" he mused.

"To have the chair, the paintings and all the other artifacts coming from Baltimore to our cathedral, I can't think of a more appropriate and striking way to demonstrate the strong link between two sides of the continent."

Representatives from the Getty, too, say they were pleased to sponsor a lecture about the basilica.

The Getty Trust schedules lectures about significant conservation projects around the country, from Frank Lloyd Wright's Fallingwater residence in western Pennsylvania to the cliff dwellings of Mesa Verde National Park in Colorado. The restoration of Baltimore's basilica clearly meets that description, said Jeanne Marie Teutonico, associate director of the Getty Conservation Institute.

"This is a building that was worthy and a project that was worthy," she said. "There are connections to Latrobe, Thomas Jefferson, the U.S. Capitol, the first American bishop - a lot of firsts."

'Worth restoring'

"The basilica is getting the recognition that it deserves," agreed Barbara Hoff Delvac, a historic preservation consultant in Los Angeles and former executive director of Baltimore's Commission on Historical and Architectural Preservation. "It is probably one of the most important buildings in the country. At least Baltimore has recognized that it's worth restoring."

Ruth hopes that promoting the basilica nationally will help show Baltimoreans how much it's valued by others.

"We have to show the people in Baltimore that it's respected by people outside Baltimore before they will respect it themselves."