MARION — Marion’s “ghost block,” where 19th-century buildings once stood but now is home to a mostly vacant strip mall primed for redevelopment, presents a stark contrast to the structures immediately north and west — vestiges of the days a century ago that Marion served as the heart of Linn County’s government.Today, Marion’s Uptown District still is splashed with history, dotted with buildings as old as 1850 surrounding City Square Park, part of the city’s original 1839 plat when it was chosen as the county seat.