Gunpowder Falls State Park spans six areas in northeastern Baltimore County and western Harford County, covering 15,088 acres along the Big and Little Gunpowder Falls and the Gunpowder River. Established in 1959 and expanded through land purchases beginning in 1960, it was created to protect the watershed through a system of river corridors and recreation areas rather than one compact tract. Its varied landscapes include tidal marshes, rugged inland slopes, trails, wildlands, boating access, and waterfront recreation. The park also includes historic places such as Jerusalem Mill Village and the site of the 19th-century Joppa Iron Works, blending conservation, outdoor use, and local history.