Montgomery County gained more than 28,000 new housing units over the last decade, according to U.S. Census figures. It had the second-largest growth in the state, fewer than 400 units behind Chester County.  The greatest growth was along Route 422, with Upper Providence Township leading the way.  It gained more than 2,000 units.  Limerick was in second place, with nearly 1,800, and Skippack, New Hanover, Lower Providence and Lower Salford also had gains of well over 1,000 units.