Gemini 4 was launched on June 3, 1965, from Cape Kennedy, Florida, and lasted nearly four days with astronauts James McDivitt and Edward White on board. This mission was pivotal as it was the first multi-day crewed mission for NASA under the Gemini program, a series designed to develop the capabilities needed for future Apollo missions aiming for the Moon. The primary objectives centered around demonstrating prolonged space travel, evaluating life-support systems, and enhancing spacecraft handling during orbital maneuvers.

One of the most memorable moments from the flight was Ed White's spacewalk, which became a historic first for American astronauts. White exited the Gemini capsule using a handheld maneuvering unit and floated outside the spacecraft for approximately 20 minutes. His spacewalk allowed NASA to test the equipment and procedures that would be critical for future extravehicular activities (EVAs) in space exploration.

The mission concluded with a safe re-entry and splashdown in the Atlantic Ocean on June 6, showcasing the effectiveness of the crew's training and the spacecraft's design. The successful execution of Gemini 4 strengthened the United States' position in the space race against the Soviet Union, demonstrating advancements in technology and human capability in space travel. The experience gained from this mission paved the way for subsequent missions, including the Apollo program, and significantly contributed to expanding human presence in low Earth orbit and beyond.