From there, twin transmission lines would carry 500 kilovolts each to a new substation to be built in Kemptown, Md.
The line's precise path has not been determined, but it could cut across southern Washington County, Allegheny Power spokesman Todd Meyers said.
"We're asking people to fill out questionnaires and surveys, and we'll use that information when we try to figure out where to put this line," Meyers said.
Allegheny held a similar public meeting Tuesday night in Frederick County.
In August, the power company will hold another series of public open houses in which people will be able to see several possible routes for the line.
More than 20 Allegheny Power employees were at the meeting Wednesday night, armed with maps, examples of tower structures and other information in an effort to answer people's questions.
Allegheny Power's Kristy Flavin pointed to a map of existing transmission lines as she talked to Boonsboro resident Denise Horner.
"In some places, it could go on top of what we've already got," Flavin said, noting that it might be possible to route the new transmission line along the path of existing lines.
Horner and others said they like that option because it seems to be the least disruptive.
"It probably makes the most sense that way," said Bethany Haner, who lives on Alternate U.S. 40.
Other people at the meeting said they were concerned about preserving parks, Antietam National Battlefield and other environmentally sensitive and historic areas.
Allegheny Power and American Electric Power, which will share a portion of the 290 miles of lines, have been studying potential routes and are accounting for cultural and historic places, wetlands and endangered species and plants, Meyers said.
The companies will finish these studies and apply for regulatory approvals from the Maryland and West Virginia public service commissions by the end of this year.
The $1.8 billion power line is needed to accommodate rising demand for electricity and prevent blackouts projected as soon as 2012, according to PJM Interconnection, a nonprofit agency that controls the electricity grid in 13 mid-Atlantic states and Washington, D.C.
PJM authorized the construction of the PATH line in June 2007.
Allegheny and American Electric hope to finish building the line by 2012.
Keedysville-area resident Bill Bradley said he understands that the line is necessary and appreciated the meeting.
He said Allegheny should hold a presentation and public forum after a final route is chosen, however, which the power company has not planned to do.
"This is informative, but with a public forum you have people asking questions that other people might not have thought of," Bradley said. "It creates more group communication that you don't have here. So it would be nice if they did that."