Pope Francis marked a "day of reflection" for the soon-to-be canonized Junípero Serra by celebrating Mass at the Pontifical North American College, lauding the 18th century missionary who worked to defend the native people against the abuses of colonialism.

"He was one of the founding fathers of the United States, a saintly example of the Church's universality and special patron of the Hispanic people of the country," the Pope said in his May 2 homily.

Through Father Junipero's witness of holiness, "may all Americans rediscover their own dignity, and unite themselves ever more closely to Christ and his Church," he said.

Saturday's Mass at the PNAC marks Pope Francis' first visit to a seminary following his 2013 election. It is also the first time a pontiff has gone to the Rome-based seminary for the United States since Saint John Paul II's visit in 1980.

The celebration was part a "Day of Reflection" hosted by the PNAC for Blessed Junipero Serra, who the Pope will canonize on Sep. 23 during his Apostolic Journey to the United States.

Born Nov. 24, 1714 in Spain, Father Junípero Serra played a key role in the evangelization of 18th century California. The missions he founded took in thousands of Native American converts to Christianity and taught them technological development skills.

Father Serra helped establish the California missions in the 1700s, many of which became the centers of major cities like San Diego.

He was beatified Sep. 25, 1988 by Saint John Paul II.

Presiding over Mass in the PNAC's Immaculate Conception chapel, Pope Francis based his homily on the day's first reading from the Acts of the Apostles which demonstrates the "missionary nature of the Church."

"This was true also for the many missionaries who brought the Gospel to the New World and, at the same time, defended the indigenous peoples against abuses by the colonizers," he said.

Father Junipero Serra was among the Franciscan missionaries who brought the faith to the Americas, he said, ushering "in a new springtime of evangelization in those immense territories, extending from Florida to California, which, in the previous two hundred years, had been reached by missionaries from Spain."

Reflecting on the life of Junipero Serra, Pope Francis described him as a "tireless missionary."

He was driven to leave his homeland, he said, by "the desire to proclaim the Gospel ad gentes, that heartfelt impulse which seeks to share with those farthest away the gift of encountering Christ:" a gift that he had first received and experienced in all its truth and beauty."

Missionary disciples, like Father Junipero, challenge us, the Pope said. Having encountered Jesus, they were "moved by the grace of the Holy Spirit, (they) went out to all the geographical, social and existential peripheries, to bear witness to charity."

Pope Francis asked whether we possess the same "generosity and courage" to respond to the same call to worship and follow God, "to rediscover him in the face of the poor, to proclaim him to those who have not known Christ and, therefore, have not experienced the embrace of his mercy."

Pope Francis also spoke of Blessed Junipero's devotion to Mary, having entrusted his missionary activity to her – in particular Our Lady of Guadalupe, the image of which accompanied him on twenty-one of his California missions.

Our Lady of Guadalupe cannot be separated from "the hearts of the American people," he said, as "she represents our shared roots in this land."

"She always hears and protects her American children."

Looking ahead to the Extraordinary Jubilee year of Mercy, set to begin Dec. 8, the Pope appealed for his intercession, and that of the many other North and South American saints.

"May a powerful gust of holiness sweep through all the Americas," he said.

Pope Francis concluded by appealing to Our Lady and these saints as he prepares for his visit to North and South America later this year.

"I ask Our Lady of Guadalupe, Friar Junipero and all the American saints to lead me and guide me during my approaching apostolic journeys to South America and North America."