PORTLAND – The First Parish Unitarian Universalist Church, Portland’s oldest church, has a tradition of embracing its 335-year history while working to initiate change.

The church’s outer gardens have, over time, served as a pathway for meditation by day and a sanctuary for transients to lay their weary heads at night. Perhaps that contrast best exemplifies what congregants perceive as their church’s role in society: to provide a place for inspiration and adaptation that supports a diversity of lifestyles in an ever-changing world.

Also symbolic of that ideal is a cannonball-embellished chandelier hanging in the church’s parish hall. The cannonball, fired on the church by British troops in 1775, bounced off its outer walls and was saved as a token signifying resilience in troubled times.

On Sunday, First Parish congregants will install yet another fixture that they hope will reflect their ideals for future generations to ponder. For the first time in the church’s history, it will install a called and settled female minister.

The Rev. Christina Sillari was unanimously voted into office in September after a nearly year-long search that included 30 interviews and as many meet-and-greet visits conducted by the church’s search committee.

Sillari will replace the Rev. Tim Jenkins, who died in 2009 after a two-year battle with cancer.

Search committee chairman Jeff Logan likened the selection process to an online dating service that ended in a happy marriage of philosophies. After exchanging long profiles detailing their respective personal histories, Sillari and the congregation met and discovered commonalities that they believe will make for a lasting relationship.

Sillari, 47, is a Massachusetts native from a working-class family of Greek Orthodox and Catholic heritage. She rejected those faith-based traditions as a teenager, becoming an atheist.

She embraced Buddhism and the ways of Eastern philosophy while attending Boston College, incorporating those beliefs into her pursuit of a master’s degree in psychology and yoga. She became a Unitarian in her mid-20s after attending a service preached by a female minister at the Arlington Street Church in Boston.

“My thoughts, then, were that ministry belonged (exclusively) to men,” said Sillari. “I remember feeling so blown away and empowered by her sermon.”

Sillari went on to serve as a youth director in the Unitarian Church for seven years before attending the Andover Newton Theological School outside Boston. She said Unitarian Universalism’s willingness to let individuals define their own brand of faith helped her theology to evolve. That open-mindedness drew her to Portland’s First Parish congregation.

“They are open to transforming themselves while allowing me to evolve in my life,” Sillari said. “That is what binds me to them and them to me.”

Logan said the search committee was drawn to Sillari’s “sense of heart, authenticity and an interest in bringing people together.”

Since Sillari’s arrival at the church, there have been noticeable changes. A Sudanese group leads worship in Arabic on Sunday mornings, and attendance is up from 120 in August to about 150.

A bonus is the appeal that Sillari brings for young families. She is married and has a 10-year-old daughter.

Logan likens Sillari’s appointment to “a sense a rebirth.”

“Our church had developed an inward, insular way of doing things,” he said. “With Christina, we are taking a step away from a somewhat staid past and trying to reinvent and re-create the relevance of this kind of alternative or liberal faith community.”