In a couple of weeks, America turns 250. In the midstate and beyond, festivities are planned for the days leading up to the Fourth of July and, of course, the holiday itself. That includes Harrisburg’s July 4 Food Truck Festival at Riverfront Park from 1 to 9 p.m. on Independence Day. As America’s semiquincentennial — a long name for the 250th — approaches, here’s a sampling of how Harrisburg celebrated the holiday in the past and how those commemorations reflected the city’s changes over time.