Cannonballs and shrapnel remain embedded in a few of the roughly 200 buildings that remain from the period.
Many of the businesses in the rural county seat cater to the throngs of tourists that stream into one of the country's most historic places, from General Pickett's Buffet to Abraham's Lady, a battle-era clothing shop.
And residents can be eager to share their expertise — and their pride.
"To have one of the most iconic battles in the history of our country or the world to take place here and to have this historical heritage in our community is wonderful," said Randy Phiel, the county's top elected official and the logistics manager of an annual re-enactment. "This opportunity won't come again. It's our Olympic moment."
Gettysburg was a quiet backwater in the mid-19th century, but roads connected it to all points on the compass, including south, where the Confederate Army under Gen. Robert E. Lee had launched his army to take the war to its northern opponents.
With a population of 2,400, about one-third its current size, the town was dominated by the carriage industry when war broke out, said Bob Alcorn, a 73-year-old Air Force veteran who leads walking tours of the town. The story that Confederates arrived in Gettysburg looking for shoes appears to be apocryphal, as there was not a single shoe factory in Adams County — though there were 30 in neighboring Franklin County.
What it did have was a location on the road to Harrisburg, the state Capitol, along with three newspapers, two telegraph units, two brickyards and a rail spur that connected the town to Hanover Junction, 15 miles east, and strong trading ties with Baltimore, 60 miles southeast.
Alcorn shows visitors the third-floor rooftop where Union Gen. O.O. Howard monitored the fight, a corner where a townswoman used a mirror to help signal soldiers to safety and a building where some legal maneuvering by noted abolitionist Thaddeus Stevens helped an academy's founders get their hands on a tax-sale property.
A block from the square, a tiny graveyard holds the remains of Edward McPherson Woods, a 3-year-old boy who died July 6, 1863, after being shot by his toddler brother with a military musket. Edward was among several local children killed by abandoned weapons and ordnance after the armies had moved on.
Another battle relic is the row of war-era houses on High Street where Gettysburg residents trapped between the lines took in severely wounded soldiers from a church that had been converted into a hospital. These days, most of the Civil War hospitals in Gettysburg — and there are many — are marked with simple red flags.
Richard Waybright, 83, whose family owns Mason Dixon Farms Inc., an enormous dairy operation outside town, is old enough to remember the battle's 75th anniversary in 1938. He heard his grandfather recall how the invading army cleaned out the smokehouse, paying for the hams with Confederate dollars.
At the time of the war, Gettysburg was home to Pennsylvania College, and a small number of its 116 students had stayed behind for summer classes despite the arrival of the rival armies. When the real shooting began, the students were quickly dismissed, and the main building — which today houses the Gettysburg College administration — also became a field hospital.
College President Janet Morgan Riggs said its history is becoming a bigger presence on campus. Students can now minor in Civil War-era studies, the college runs a Civil War institute that attracts scholars each summer and, for the past 11 years, freshmen have been brought to the national cemetery to hear President Abraham Lincoln's "Gettysburg Address" and other speakers.
"For a period of time, we did not embrace this historical context," Riggs said. "I don't know if there was a fear we'd be seen as a Civil War college, but over the last couple decades we have certainly embraced it."
These days, Gettysburg can feel a bit like an open-air museum, with people walking its streets in period garb. One reason for the lost-in-time feel is the park itself, which surrounds the town and chokes off much of what would certainly be miles of suburban development. A strip of development runs eastward on Route 30, but anyone hoping to build on land that can be seen from the park can run into preservation regulations.
The park offers locals the use of some 30 miles of bucolic roadways and vast open spaces as well as a constant string of cultural events, both on and off park property. About 400 such events are scheduled for June 28 through July 7.
The stream of visitors can put a crush on police, sanitation, road maintenance and emergency services.
The Gettysburg Convention and Visitors Bureau estimates visitors spent $605 million in 2011, generating $115 million in tax revenues and supporting 7,500 jobs.
"Most of the tourist-related jobs are lower-paying," Phiel said. "They aren't necessarily career-type situations."
Tourism is the region's top industry, rivaled in size only by the fruit orchards that were established after World War I. Many of its residents commute to nearby towns for work, and retirees have moved in, drawn by its rural nature or a love of the Civil War.
As retirees move into the area from Baltimore and Washington, Waybright worries about the younger generation. Many county schools have experienced declining enrollment over the past five years, and half of his 17 grandchildren "headed to the big city" to find careers.
"We're now over 100,000 (population)," Waybright said. "But it's awful, what's happening to our schools."