Many events will coincide with Pope Benedict XVI's visit to Washington and New York from April 15 to April 20.
"During his visit, our Holy Father will commemorate an important date in the history of our local church and the church in the United States: April 8, 1808," O'Brien said at a news conference to outline the events for bicentennial. "The Archdiocese of Baltimore will be represented in Washington and New York when the pope honors this important anniversary."
According to Pope Benedict's official itinerary, he will meet with President Bush and American Catholic and other religious leaders, and speak at the United Nations. He will visit Washington from April 15 to April 17 and New York from April 18 to April 20.
"I think we'll get a good read on our faith and culture in the United States of America from a very perceptive outsider," O'Brien said of his expectations of the pope's visit.
O'Brien said the Baltimore Archdiocese made tickets available on its Web site last month so that Baltimore-area Catholics could attend Masses at Yankee Stadium in New York and at the new Washington Nationals stadium.
The church made 1,000 tickets to the April 20 New York Mass available to members of the Baltimore Archdiocese, and 2,500 tickets for the April 17 Mass in Washington. The tickets sold out in an hour, but 500 are reserved for youth groups for Washington.
O'Brien said that excitement over the pope's visit is "hard to gauge right now," but he expected it to build as the arrival date approaches.
Benedict is to meet with President Bush on April 16, the pope's 81st birthday. The pontiff also plans to visit the site of the 2001 attacks on the World Trade Center.
Apart from the pope's visit, Baltimore church leaders have planned events to celebrate the elevation of the diocese to archdiocese status two hundred years ago.
On April 11, the archdiocese will hold a groundbreaking for a new prayer garden that is being built at the former site of the Rochambeau, a 100-year-old apartment building that was demolished over the objections of preservationists.
An exhibit about the archdiocese's 200-year history will be presented at St. Mary's Seminary in North Baltimore the next day. Musical performances at the Basilica are also planned for April 13 and June 1.
On April 13, O'Brien will celebrate a bicentennial Mass at the Basilica, after which he will dedicate a bust of Cardinal William H. Keeler, Baltimore's previous archbishop. Lectures are also being planned in April, May and June. They will focus on the founder of the archdiocese, John Carroll; on papal history; and young adults' relationship with the church.
Tricia Pyne, an archival director at St. Mary's Seminary in North Baltimore, is helping to organize the exhibits, which will include some of Carroll's personal papers that date to the late 1700s.
"I like to say that John Carroll was to Catholicism in this country as George Washington was to the founding of this country," Pyne said. "The foundations he laid were built upon over the next 200 years."