MARIETTA — The Rev. Roger Allen has only been rector of St. James’ Episcopal Church in Marietta since December, but already he has mastered the necessary skill of timing his Sunday sermons that his 24 predecessors learned as well.

Whenever a train comes roaring through Marietta Square, Allen said he has to quickly decide how much time he has to finish the next line of his sermon. Fortunately, it only happens once on Sundays and sometimes the engineers will lightly sound their whistles in courtesy to Church Street worshippers, he said.

It’s all in a day’s work for the rector of one of Marietta’s oldest churches, established by many city founding fathers.

On July 29, St. James’ will celebrate its 170th anniversary with a special 10:30 a.m. service. Afterward, there will be flamenco music, tapas food and activities for adults and children with Spanish fare in the Parish Hall.

The Spanish theme is derived from the church’s name, which along with its official yellow and red colors, are a nod to St. James, patron saint of Spain.

“We decided that we would focus this celebration this year on St. James Day and begin again a tradition of celebrating the founding of this church with the special intention of building toward the 175th celebration,” Allen said.

On July 29, the worship service will contain music with historic ties to St. James and a festival Eucharist, which will involve more pomp and circumstance than a regular service, Allen said. The scripture readings will also be related to St. James, one of Jesus’ closet disciples.

“St. James played a huge role because he was one of the first few disciples called,” said the Rev. Daron Vroon, associate rector. “He saw the transfiguration of Jesus on the mountain top, the raising of the 12-year-old girl who had died, and he was there at the agony of the garden the night before Jesus died.”

In 1842, St. James’ was founded by many of the engineers who constructed the railroad between Atlanta and Chattanooga, according to church history. William Root, who opened Marietta’s first pharmacy, asked that the new church be named for his home church of St. James in Philadelphia.

In 1849, a cemetery was established on the furthest corner of the church’s then 20-acre property at the corner of Winn and Polk streets. In 1850, burials began and continue to this day.

The church continued to grow and faced financial hardships through the Civil War and World War II. In January 1964, a boiler room fire destroyed much of the church building, which was rebuilt three years later. In 1972, St. James’ Day School was established as an independent private school and named after a rector, the Rev. Joseph T. Walker.

Today, St. James’ congregation of 1,200 members is involved in community activities ranging from a Sunday Sack Lunch program, Wonderful Days Pre-School for low-income families and Habitat for Humanity, to the operation of the St. James Church Thrift Shop on Washington Avenue.

“There’s a combination of the really old Mariettan families that go right back to the beginning in the 1830s and the newcomers who have come in from companies that transferred them to Atlanta,” church historian Michael Campion said of the present congregation.

“It’s a complete spectrum of a whole range of people. That range has gotten bigger over the last 30 years. Most of the old people have adapted as well as the new ones.”

Vroon said the people of St. James’ manage to remain rooted in the church’s history without being stuck in the past.

Born in Thomasville, Allen practiced maritime law in New Orleans before answering the call to the priesthood in that city. He worked in the aftermath of Hurricane Katrina and later in Alabama, before coming to Marietta.

“I’m the 25th rector in 170 years,” said Allen. “That to me is an astounding testament to the people who are in this church.”

Allen said his future plans for St. James’ include expanding worship service offerings and its mission work in Marietta and around the world.

“The main thing I want to do is get the word out that this is a really wonderful and special place to be,” he said. “It’s a place where you are encouraged to grow your faith and spirituality as the Holy Spirit is leading you.”