On Murphy's Farm, Confederate Gen. A.P. Hill led a flanking maneuver that allowed for the capture, Civil War experts say.
Although Murphy's Farm was added to the park after the land preservation group purchased it, there are other large land parcels in the area that were preserved but cannot be added to the park.
The land cannot be added because the park has reached its maximum allowable size of 2,505 acres.
There is a proposal pending before Congress to increase the park by another 1,299 acres. Allowing the park to expand by 1,299 acres means it could accept properties, including about 176 acres in the School House Ridge area, which recently was purchased by the Civil War Preservation Trust.
Another parcel that would be added to the park includes 375 acres in the Loudoun Heights area that was donated to the park several years ago by a Silver Spring, Md., couple.
Members from a number of organizations who support the park expansion - including the Harpers Ferry Conservancy, Friends of Harpers Ferry National Park and the Civil War Preservation Trust - joined Capito for a tour of Murphy's Farm and asked for her help in expanding the park.
Park supporters briefed Capito on the effort to protect land around the park as she stood on an overlook above the Shenandoah River.
Although some of the properties in the 1,299-acre area have been set aside for the park, other land is in private hands and is under development pressure, park expansion supporters said.
"We need a champ in the House. We wanted you to see this," said Matt Ward, a Charles Town City Council member and member of the board of directors of the Harpers Ferry Conservancy.
Given the area's history and the educational value it can serve, Capito said she supported the expansion effort.
"You can certainly count me in your corner. I've always thought of this as the gateway to West Virginia," Capito said, drawing a round of applause from the group.
After the meeting, Capito said the effort to expand the park's boundaries would require work to balance the interest of developers with those who want to expand the park.
When asked how difficult the effort would be, Capito said, "Everything is difficult. But we have a jewel here."
Ward said time is of the essence because growth is occurring quickly.
The pressure includes a proposed sewage treatment plant larger than the size of Charles Town's sewer plant, Ward said. The plant would be built on a tract close to Murphy's Farm, Ward said.
"The barbarians are at the gates," Ward told Capito.
Park Superintendent Donald Campbell told Capito he thinks there is a lot of public interest in expanding the park.
"I've been looking at this for a long time," Campbell said.