Final answer:
Alan B. Shepard Jr. was the Navy officer who made America's first suborbital flight aboard the Mercury Freedom 7 mission on May 5, 1961.
Step-by-step explanation:
America's first suborbital flight was made by Navy officer Alan B. Shepard Jr. On May 5, 1961, Shepard piloted the Mercury Freedom 7 mission and became the first American to travel into space. This event marked a critical moment in the Space Race between the United States and the Soviet Union. While the Soviets had already achieved significant milestones, including the first human in space, Shepard's suborbital flight symbolized a pivotal step for NASA's Mercury program and the United States' commitment to winning the space race.