Ronald Reagan's birthplace, a second-story apartment over what was once a small-town tavern in Tampico, Ill., is today marked by a museum. John Adams' birthplace is a national park. Even Rutherford B. Hayes, whose birthplace is today covered over by a BP gas station, merits a metal plaque commemorating the location. But while most of America's 44 presidents have tourist attractions or monuments of some kind marking their birthplaces, President Barack Obama – for several reasons – may not be granted the honor. Three obstacles in particular stand in the way: First, though Obama maintains he was born in Honolulu,...