Not just any inmate can participate in the program, Maynard said. To be eligible, prisoners must have committed less-serious crimes, be nearing release, and earn their way into the program. They earn "a dollar or two" a day for their labor, officials said.
Maynard said the inmates who worked around Antietam "probably didn't know the history of the Civil War."
"They didn't know what sacrifice was made, for both sides, for saving the Union and state's rights," he said. "So all of a sudden, they're a part of history. That's going to help them change their mentality and what they're worth as a person."
Maynard credited outgoing Baltimore Police Commissioner Frederick H. Bealefeld III for suggesting Mount Auburn as a potential project. Bealefeld watched Monday's event with his staff, under some trees far from the assembled press and public officials. He declined to comment, saying he wanted attention to focus on the corrections department and the inmates.
The inmates who worked most recently on Mount Auburn cemetery were allowed to attend Monday's event, and shook hands with O'Malley.
During their time on the project, prisoners attended services at Sharp Street, and church members brought them food during their shifts.
Inmates said they found the response from the community fulfilling.
"What are you getting out of sitting in a prison cell?" asked Michael Toder, a 35-year-old from Charles County who is nearing release for a sentence for arson, according to court records. "Something like this gives you an opportunity to give back, to pay your debt back."
Johnson, a member of the Mount Auburn Cemetery board of directors who performs research to help people locate graves of their loved ones, said the inmate labor was "a blessing" for everyone involved.
Supporters of the project say their work is not done: Grave markers need to be straightened out, and some graves remain unidentified. The grass will continue to grow; the weeds will come back.
The Abell Foundation kicked in $90,000 for the project. Jeanne Hitchcock, the chair of the Mount Auburn Cemetery board of directors, said the church is focused on creating an endowment.
"One of the impediments [to creating an endowment] has been that people didn't see any progress," Hitchcock said. "Now that we've taken that giant step of clearing it up and getting partners involved, we can talk about sustainability. What we cannot do at this point is lose ground."
When Sherman Harris first saw the church grounds in 1988, he cried.
The 77-year-old Potomac man, a volunteer with the United Methodist Church, helped on various efforts over the years to clean up the grounds.
"I'm a person of faith," Harris said. "But I didn't think I'd see it in this present state."