The sign accompanying the Gemini
4 hatch. It reads
Gemini 4 Spacecraft Hatch
Edward H. White left the Gemini 4 spacecraft through this hatch, June 3, 1965.
He was the first American to walk in space. This first Extra Vehicular
Activity, or EVA, was a critical step on the way to the Moon.
On Loan: National Air & Space Museum
Despite what the sign says, the hatch through which Ed White traveled to
perform the first EVA is actually still attached to Gemini 4 at the
Smithsonian; the pilot (who performs the EVA) sits on the starboard side
of the spacecraft, while the command pilot sits on the port side.