The Portland-class cruisers originally had 1-inch (25 mm) armor for deck and side protection, but in construction[8] they were given belt armor between 5 in (127 mm) (around the magazines) and 3.25 in (83 mm) in thickness.[11] Armor on the bulkheads was between 2 in (51 mm) and 5.75 in (146 mm); that on the deck was 2.5 in (64 mm), the barbettes 1.5 in (38 mm), the gunhouses 2.5 in, and the conning tower 1.25 in (32 mm).[10]