At Fort McHenry, even in winter, Greg McGuire and his platoon have enough work to keep busy from dawn's early light to the twilight's last gleaming.
Their orders: to defend the fort against aging, the elements and a human tide that scours every surface, from grass to glass, and compresses the earthworks.
The number of visitors always increases as spring approaches, and the fort's National Park Service protectors have mixed emotions about this year's coming invasion.
"The British were a one-shot deal," says Mr. McGuire, the maintenance chief, but tourism is relentless and "can be an even bigger challenge than what the elements do to the place."
"This fort never was intended to support 500,000 folks a year," says ranger Paul Plamann. "This is a real problem, and it's a problem across the National Park Service.
"You want to invite people in to enjoy the area, but we also have a mission to preserve it so future generations can enjoy the same things."
Fort McHenry had a boom year for attendance in 1994, with 576,467 visitors, but the pounding of so many feet takes a toll on the earthen ramparts that withstood the British bombardment of 1814.
Damage to the sod helps weaken fortifications that 1,500 to 1,800 shells and rockets could not defeat, says Vincent Vaise, one of eight rangers at the fort.
"These walls [accumulate] water like the Hoover Dam," he says. "This is an earthen fort; the water is inside and out."
Completed in 1802 and named for a distinguished Baltimorean who raised funds for it, Fort McHenry is a star-shaped post occupying 43 acres of Whetstone Point in South Baltimore. Walls of brick and stone serve as a dike to hold the earth in place.
The erosion atop the fort aggravates the problem of moisture within, says Leonard Simpson, an architect and national trouble-shooter for the park service.
OC Water saturates the earthworks, and its constant hydraulic pres
sure, coupled with freezing, has caused the retaining walls to bow and buckle in many places, Mr. Simpson says.
He is in Baltimore to help supervise major restoration work on the brick perimeter by an outside contractor. It is a painstaking, two-year, $1.5 million project.
Meanwhile, regular maintenance goes on in all seasons. Mr. McGuire, who has worked at the fort for 22 years, has a full-time staff of 12 -- masons, mechanics, groundskeepers and a horticulturist -- and an annual budget of about $500,000.
It is unheralded but vital work, because the wave of humanity that passes through the arched entrance abrades every surface that can be touched or trod upon -- sod, stone, brick, glass and wood.
He and his squad patrol the fort and its six wooden buildings to scrape, paint, hammer and saw. They wash and weed the outer walls, removing moss and other greenery. They tend the 2 miles of brick walkways and trim the vegetation. (The earthworks are covered with special grasses to combat erosion.)
This winter, the staff has painted the walls of the guardhouse, mended broken windows in the officers' quarters and repaired rotting porch columns above the barracks.
Guarding the fort is "a passion for us," Mr. McGuire says while inspecting a wall for algae. "Most of my crew have been here since the Bicentennial [in 1976]; they feel real close to this place."
Vandalism is almost unheard of, but "visitors are curious; they're touchy-feely," he says. "They wear away the paint real fast."
Tourism was particularly heavy last year. From 1990 through 1994, the fort averaged 562,094 visitors annually, and the 1994 total was 14,373 above that level.
Translation: On an average day, about 1,500 people come to inspect, study, enjoy and roam around a fort whose 19th century occupants were kept off the earthworks to reduce erosion.
"In the old days, soldiers had restrictions on where they could walk; ramparts were off-limits," says Mr. Plamann, a ranger at Fort McHenry for 27 years.
Similar rules govern tourists today. Signs forbid climbing on the cannons and the earthworks. And letters sent to school groups, as part of their pre-visit packages, caution that the fort is not as solid as it looks.
"Kids come here, get turned on and don't understand the fragility of what appears to be such a super structure," Mr. Plamann says. "They see the stone and brick and mounds of earth that are supposed to be impenetrable.
"But the fort can be broken down. This fabric can receive stress and strain to the point where it collapses."
When spring rains come, he says, the sod slips, and earthworks can turn to mud.
"In summer, we have joggers, picnickers, kite fliers, dog walkers," Mr. Plamann says. "The ramparts give a great view of the harbor, if you get up there and look all around."
But all of that foot traffic contributes to still more erosion.
"Originally, the fort was meant to keep people out, rather than inviting folks in," Mr. Plamann notes.
In 1814, Fort McHenry pulled off what amounted to a historical double play -- a feat Congress acknowledged 125 years later by giving the fort unique status.