For 100 years, Aberdeen Proving Ground has been a major economic and social force in Harford County and a new exhibit, APG as Catalyst: Harford County’s Changing Landscape, opens on Tuesday, Feb. 7, at Harford Community College to commemorate the anniversary with “a scholarly, balanced and humanistic exploration of how APG’s presence has shaped the lives, histories, economy and culture of Harford Countians.” The exhibit will be open from 1 to 7 p.m. in the Hays-Heighe House at Harford Community College.