It lasted about two hours, and strangers who sat through it together became friends. They shook hands during the sign of peace with heartfelt affection and recited the "Our Father" with eyes riveted on the leader of the world's 1 billion Catholics.
Of course, turning a baseball stadium into a cathedral made for some odd and less-than-spiritual touches: Cameras clicked constantly, people left their seats for coffee and soda and, on the club level, a few exhausted stadium workers snoozed during the homily.
"It's much easier than a ballgame -- there is no beer," said janitor Gwendolyn Parker as she swept paper and cigarette butts from a remarkably clean floor. "And there's no peanuts."
At 11:15 a.m., about a half-hour behind schedule, trumpets blared the entrance hymn. Five minutes later, the pope kissed the linen-draped plywood altar.
Before it was over, tens of thousands of people would receive Holy Communion. Rehearsals had allotted seven precise minutes for the distribution of communion, but it took closer to 12.
Most received the Eucharist from priests and lay ministers, but 60 people -- including Deborah Holly of St. Peter Claver parish in West Baltimore -- received it from the pope himself.
Noting the deliberate manner with which the pope took the consecrated wafers from the ciborium before presenting them, Ms. Holly said: "He actually held it in my hands for a moment."
Before the service, the Archdiocese of Baltimore mounted an on-field celebration for the pope that could not have been more spectacular: Picture Greek and Polish folk dancers kicking up their heels to a soaring African-American gospel choir.
Yet the program was overshadowed by a roar of applause every time the huge screen in center field broadcast live shots of the pope as he approached Baltimore.
About 10 minutes to 11 -- to the pounding pop rhythms of Boyz II Men -- the pope rode onto the home field of the Baltimore Orioles, circling the warning track in his popemobile to huge applause.
People jumped and waved and screamed as he rode by each section of the standing-room-only crowd of 50,000. The pope waved and made subtle signs of the cross. His rugged face -- reminiscent of working-class Poles from the Southeast Baltimore waterfront -- looked stern and serious, his eyes narrowed in the glare of the sun.
Just before 11 a.m., he made it to the center field altar and climbed down from his car. The faithful, now hushed, were treated to the sight of Maryland state troopers bending to kiss the pontiff's ring. Many stared at the JumboTron in reverent awe, clutching to their chests the white and yellow Vatican flags they had been waving.
Cardinal William H. Keeler ended a lengthy welcome by repeating a phrase the crowd had been showering the pope with all morning: "Pope John Paul Two, we love you."
Scripture readings came from the Old Testament prophet Habakkuk, a letter from St. Paul to Timothy -- delivered in Spanish -- and the gospel of Luke, the last of which was read by Maryland native John Messina, a lawyer turned seminarian.
The pope referred to all three readings in a homily that quoted Abraham Lincoln's doubts whether a just America could "long endure," said the same questions face the nation still, and went on to call this country's youth to the missionary life.
At 12:42, after the offering was taken in cardboard boxes, the pope raised the consecrated host before all. A moment later, he did the same with a chalice of wine.
Quoting Christ, he said: "Do this in memory of me. . . ."
After the Mass, the pope took time to greet each of the 200 bishops in attendance.
"This is a pope for the ages," said Bishop John D'Arcy of the Fort Wayne-South Bend, Ind. diocese. "We won't look upon his like again."