Both girls plan to go to Harford Community College, and Jamie wants to pursue early childhood education while Janey will study general education because she will be moving out of state.
Janey said she was mostly "nervous about people," explaining she was anxious about walking across the stage.
She also said she felt "relief" about finally graduating, while Jamie said she thought it meant "starting our adult lives."
Other state and local officials also wished the graduates well.
One was Harford County Councilman Dick Slutzky, who represents Aberdeen and who has not missed a graduation since 1973, Principal Michael O'Brien said.
He advised students to investigate everything, learn just for fun and not think they are smarter than the rest.
State Del. Glen Glass recalled the many unique aspects of Aberdeen, like the Bush River, Chesapeake Bay, Ripken Stadium and "friendly, hard-working people."
Board of Education member Thomas Fitzpatrick, meanwhile, gave his first graduation speech at Aberdeen.
"Whatever you choose, always remember that the choice is yours and yours alone," he told the students.
Maj. Gen. Robert Ferrell, the senior commander at Aberdeen Proving Ground, was also sitting on the stage, as state Sen. Barry Glassman pointed out.
Glassman noted that Ferrell has reached out to Harford County and taken part in parades and community events like no one else has.
He urged students to "thank a soldier" for all of their many freedoms as Americans.