The school, in Gerrardstown in the southwestern area of the county, opened to fourth- and fifth-graders in August and will house third-graders in the upcoming school year.
Berkeley County Schools Superintendent Manny Arvon, who spoke during the ceremony, said Gerrardstown will always be special to him, since his first job as a principal was at Gerrardstown Elementary School.
On his first day, he said, two women from the neighborhood came in and welcomed him with fried chicken, corn on the cob and green beans.
There have been a lot of changes in Berkeley County since then, Arvon said, with the number of students growing by hundreds each year.
This year, more than 600 new students began attending Berkeley County schools. To accommodate the growth, a new school is built nearly every year, with seven opening since 1998. Another 13 have undergone major renovations.
While there are no plans to open a new school next year, three - Martinsburg South Middle School, Bunker Hill Elementary and Mill Creek Intermediate - are being renovated. Bunker Hill Elementary is being doubled in size, with the number of students expected to increase from 200 to more than 500, Arvon said after the ceremony.
To keep up with future projects, Arvon said that the Board of Education likely will seek a bond approval from voters "in the near future."
He said the county's next new school could be either an elementary school or a middle school.
"We need six," he said.
Mountain Ridge is the county's 29th school.
Elsewhere in the school after the dedication ceremony, student ambassadors Scotty Mock, a fourth-grader, and fifth-grader Eddie Getts were showing visitors the third-grade wing.
The student ambassadors all had informational cards from which to read to those on self-guided tours of the school, but they happily went off-script when asked.
"I like the gym and the art room," Scotty said.
"It's just fun to come here and it's got bright colors everywhere and all the teachers are really, really nice," Eddie said.