Thousands of Catholics poured onto the grass of Catholic University on Wednesday to watch Pope Francis make a Spanish missionary a saint when he celebrates Mass at the Basilica of the National Shrine of the Immaculate Conception on Wednesday in Washington, the first canonization on U.S. soil.

During the Mass, Francis will canonize 18th century Franciscan theologian Junipero Serra, who is credited with spreading Christianity in California but is controversial among some for the treatment of Native Americans under his leadership.

The pope will lead the Mass from the east portico of the Basilica, looking out on the 3.6-acre outdoor space where Catholic University holds its annual commencement ceremony. During the canonization, Pope Francis will declare Serra to be enrolled among the saints and “to be venerated as such by the whole church.”

Francis’s decision to canonize Serra is seen by Catholic Church observers as a gesture to Hispanic Catholics, and many of the tickets for about 25,000 people to attend the Mass went to Hispanic Catholics from the D.C. area. Pope Francis’s visit to the U.S. and this canonization will likely energize the Latino base of the Catholic Church in the United States, said Timothy Matovina, executive director of the Institute for Latino Studies at the University of Notre Dame.

“Hispanic Catholics feel deeply that he’s one of their own,” Matovina said. “It resonates on a very personal level, that he has this familial style. It’s a resonance of cultural style, a style of speaking of Christ not just as a person from 2,000 years ago.”

For many Native Americans, however, Serra is no saint. The Indians who joined the missions that Serra built were forced to shed their own culture, including their religion, dress and food. Thousands of them died prematurely from diseases common in Europe.

“This pope doesn’t really care what we think,” said Ron Andrade, the director of the Los Angeles City/County Native American Indian Commission and an Indian from the Lajolla Indian Reservation. “I don’t know what he is hoping to accomplish with canonizing Serra. There were better people.”

“Cesar Chavez would get more attention than this Father Serra,” Andrade said, referring to the 20th century labor leader and civil rights activist.

Treated as a hero by many in California, Serra established Catholic missions along its coast as he marched north with Spanish conquistadors. A statue of him stands in the U.S. Capitol, where each state is allowed two statues. Some historians and the Catholic Church focus on Serra’s dedication to Native Americans, while others say he oversaw and even contributed to a system that mistreated tribes.

The announcement earlier this year that he would be canonized came as a surprise to most observers. Serra is credited with only one miracle when saints usually need two (Pope Francis has said that Serra’s life serves as a second miracle). In only two years as pope, Francis has fast-tracked several candidates for sainthood.

Earlier this month, the California Catholic Conference announced that the bishops will review Catholic schools curriculum and revise displays at state missions, saying that “the Indian experience has been ignored or denied.” The vast majority of people don’t know who he was and don’t have strong opinions about who he is, said Steven Hackel, a history professor at the University of California at Riverside and author of a biography of Serra, who will attend the Mass.

“It’s an opportunity to rethink the origins of our nation, beyond just Anglo-Saxon men who worked to form a new nation,” Hackel said. “I hope we look back as a turning point, not just how we look at his life but how we look at our nation’s origins.”

Serra’s dedication to missions should challenge Catholics, Pope Francis said in a homily on May 2. “Sometimes we stop and thoughtfully examine their strengths and, above all, their weaknesses and their shortcomings,” he said.

Serra left the comfort of Majorca, Spain and became a missionary to the new world, Vatican spokesman Manuel Dorantes said while waiting for the Mass to begin.

“It’s the main reason why he’s being canonized today. Not because the man was perfect. Not because he was already walking around with a halo,” Dorantes said. “But because he felt the call to get out of himself, as the Holy Father has been calling the church — to get out of herself and become a missionary church.”

Serra already appears in a stained glass window at the entrance of the basilica, a church that attracts nearly 1 million visitors every year. The basilica is more closely linked with the Vatican than any church in the United States, according to Thomas Tweed, a professor at Notre Dame and author of “America’s Church: The National Shrine and Catholica Presence in the Nation’s Capital.”

The basilica’s building plan was approved by Pope Pius X himself in 1913, and it adjoins Catholic University, the U.S.’s pontifical school. It is also where U.S. bishops meet for ceremonial gatherings.

Tweed wonders how the pope will walk the line between praising Serra and denouncing the atrocities committed against Native Americans.

“He would be a rude guest to come in and not say good things about Serra, the new saint,” Tweed said. But he would not be speaking the truth if he completely sidesteps some of the difficult parts of history. “My hunch is he’ll try to do both things,” Tweed said.

Historians have documented the exploitation of the natives by Catholic missionaries, and in July, during a visit to Bolivia, Francis offered an apology for actions of the church during colonialism.

Catholic University, which is adjacent from the basilica, is the only U.S. university to have been visited by two popes: John Paul II in 1979 and Benedict XVI in 2008. Both popes spoke on the topic of Catholic higher education.

On Wednesday, Pope Francis met with President Obama in a private reception at the White House. He will address Congress on Thursday, becoming the first pope to address a joint session of Congress.

On Thursday evening, the pope will travel to New York, where he will address the United Nations, hold an interfaith ceremony at the 9/11 memorial, visit a school in Harlem and travel through Central Park. On Saturday, he will travel to the World Meeting of Families in Philadelphia, where he will celebrate a final Mass on Sunday.

Bonnie Berkowitz contributed to this report.

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