The Northampton requirement belongs to the Washington Treaty era, when the United States could build multiple cruiser types without an aggregate cruiser-tonnage ceiling. A comparable scout designed under the London Naval Treaty would probably carry 6-inch guns, allowing armor, speed, and armament to be balanced within the light-cruiser category. In the early 1920s, however, the Navy urgently lacked a fast scouting force after its planned battlecruisers disappeared. The flagship spaces, aircraft facilities, speed, and 8-inch reach of the Northamptons were a rational response to that specific gap even though later treaty categories made the result look anomalous.
Notable Point · 1:08:19-1:09:32
Treaty timing and lost battlecruisers created the Northampton requirement
The US Navy needed a fast scouting force after losing its battlecruisers, while later treaty rules would likely have produced a more balanced six-inch design.