The 600 Ordnance Testing Area Historic District was constructed after the 1926 Lake Denmark Naval Powder Depot explosion and several other accidents destroyed the Arsenal’s Cannon Blenders. Its facilities were built to withstand shock and blast from indoor testing of military explosives. No similar grouping of explosive testing related structures is known to exist at any other former industrial arsenals. Farther along Green Pond Mountain are a series of isolated test ranges for firing guns, armor-piercing shells and bombs, and anti-personnel weapons.