The church has come a long way since it launched in the early 1800s in a log cabin.
With a school and a new service at The John Carroll School under its belt, Luke Erickson, director of community impact, will also be starting a community center in an Edgewood strip mall, to be called The Epicenter at Edgewood.
But as Cachiaras told his congregation Sunday, the growth comes with a mission and responsibility.
"Are you going to do the Kingdom or are you going to decide, here it is and leave it there?" he challenged them as he stood in front of the map covered in red Mountain "outposts."
Size clearly does matter at the church, where parking attendants swiftly direct traffic flow onto Route 152 between each service.
Inside the New Life Center, ushers direct and coordinate the flow of hundreds of people in and out of different entrances to the cavernous sanctuary.
Sitting in a corner office on Sunday afternoon, Cachiaras was also eager to explain the church's growth in the language of a corporation.
"The easiest way to explain the multi-site concept of church is to think of it like a franchise, where we simply reproduce all that we are in another 'branch' location," he said. "So we're now a church that gathers in two locations, and after the Edgewood campus launch, we will be a church that gathers in three locations."
The ministry staff is equally aggressive about keeping things casual.
Everyone seems to be on a one-name basis. Cachiaras, the senior pastor, is "Ben" and Erickson goes by "Luke." The church is called just "Mountain."
"Mountain has been around for 189 years, so certainly there have been many changes over the years," he said.
"The buildings, the music, the growth, the way the ministry looks, these have all changed," he said, noting a pastor in the 1800s would not have been asking congregants to pull up the Bible on their iPads.
Despite that, however, "the message never changes. The methods continue to change. But methods and the packaging are not really the most important thing," he said.
His theory on why Mountain continues to be successful is its commitment to bashing stereotypes and just being honest.
"It's not a place that has a lot of pretense about it," Cachiaras said. "People feel there's an acceptance and a welcome, and they are meeting real people."
He noted it is also a place for people who are hurting, pointing out the church's Celebrate Recovery program and its participation April 217 in ServeFest, which featured 1,500 people just in Harford County working on 63 service projects.
For Erickson, the new focus on Edgewood is personal. The 31-year-old Rochester, Minn., native moved there five years ago after finishing Emmanuel Christian Seminary (the same school attended by Cachiaras, also from Rochester).
Erickson, who is white, said he was often steered away from buying a home in Edgewood, and he heard from people who were black who were, instead, encouraged to buy there.
Wearing a "Respect the Ram" T-shirt in honor of Edgewood, Erickson said he decided to buck the racial stereotypes.
"We are unsettled about the stigma that gets attached to Edgewood," he said. "We are not going to participate in Edgewood-bashing. We are just trying to see things as they are."
He and Cachiaras added plenty of people are already working in Edgewood, and Mountain has long had a presence there already.
They have taken part in Blessings in a Backpack, feeding 750 children at Magnolia, William Paca and Old Post elementary schools every weekend and partnering with Habitat for Humanity this year to fix a home in Harford Square.
"We recognize that many good things are happening in Edgewood and that many people want to see that community strengthened and improved, and we just want to come in and get on the team with those who are already doing those good things," Cachiaras said.
There could also be more in store for the Bel Air campus, and other parts of Harford, he hinted.
"We believe there are other places in the county that could use a similar campus," he suggested. "Right now our focus is to certainly get the Edgewood center up and running."
Despite presiding over one of the largest churches in the area, Cachiaras thinks one of the biggest challenges to the church is its loss of influence.
"We certainly lived in changed times, what could be described as a post-Christian society, where the church and the values of Christendom are pushed to the margins. Christians don't generally hold a place of respect like we once might have," he said. "I think there's a need to re-vision, re-express what the church is all about to bash the stereotypes and show in simplest terms who Jesus is by how we live simply in the ways he taught us."
There was little indication of that at Mountain's Sunday service, where almost every seat was filled and Cachiaras told the worshipers confidently about what they have accomplished so far.
Looking at a sea of people holding 3-D glasses for the latest sermon series, "Life in 3-D," Cachiaras was quick to say that society often sees people in the church as "a bunch of lame nincompoops."
He told a story about Tony Campolo, a prominent progressive pastor, throwing a birthday party for a prostitute he happened to run into at a Hawaii diner.
Cachiaras suggested that is the kind of church he wants.
Recalling the recent ServeFest, he told his audience: "Where do we ever see that many Christians do something together, unless it's at a concert where we sit on our rear ends and get fed?" he added. "That's what kind of church this is."