THE EMOTIONAL PULL of Gettysburg, which is about to celebrate the 136th anniversary of the epochal battle, is immense. Civil War sites in Western Maryland, from Carroll County to Hagerstown, hope to capitalize on the pilgrims drawn to Gettysburg 30 or 40 miles away.

So it's difficult to buy the argument of merchants in the Pennsylvania town that they'll be hurt if the National Park Service builds a planned $40 million visitors center a half-mile farther from the town's business district by 2003.

The argument recalls a similar fight in Baltimore a quarter-century ago when plans for Harborplace elicited howls from nearby Little Italy. If the Inner Harbor is loaded with places to eat, restaurateurs wanted to know, who'll visit us? As it turned out, the more people who came to Baltimore's revitalized harbor, the more who ventured eastward for a bite of linguine. Likewise, a more sophisticated visitors center and a restored battlefield will enhance the experience, perhaps whetting appetites to visit the picturesque town nearby.