Final answer:
The first aircraft carrier designed from the keel up was the USS Ranger (CV-4), launched in 1933, marking a significant advancement in naval aviation.
Step-by-step explanation:
The first aircraft carrier designed from the keel up was the USS Ranger (CV-4). Launched in 1933, the USS Ranger was a pivotal step forward in naval aviation and carrier design. Unlike her predecessors which were conversions from existing hulls, the Ranger was specifically designed and built to be an aircraft carrier.
While other ships like the USS Hornet (CV-8) and the USS Yorktown (CV-5) played significant roles in the U.S. Navy during World War II, with the Hornet being famous for launching the Doolittle Raid and the Yorktown participating prominently in the Battle of Midway, they were not the first U.S. Navy vessel built as an aircraft carrier from the keel up.
The concept of aircraft carriers evolved significantly after World War I and continued to grow in importance as naval aviation became increasingly crucial to military strategy. The USS Ranger represents the transition to purpose-built aircraft carriers that would define modern naval operations.