The US Navy had the ten ship Omaha class under construction when the Washington Treaty created the 8" (heavy) cruiser. To simplify building times and to steal a march on the USN's competitors, a further four hulls of the Omaha type were ordered to be armed with a new twin 8" turret that would also be mounted on the converted Lexington class Aircraft carriers.
The new heavy cruiser type were allowed a 10,000 ton standard displacement. This allowed the designers to work in another 1,000 tons of armour into the Omaha design. Speed dropped to 32 knots, but this was an acceptable speed to act as scouts and to be able to work with the fleet.
