NASA Photo ID: 65-H-438
Date taken: 03/23/65
Astronaut John W. Young, followed by Virgil I. (Gus) Grissom walk up the ramp to the elevator that will take them to the white room atop the Gemini launch vehicle. The two astronauts boarded the Gemini spacecraft on the morning of March 23 for the National Aeronautics and Space Administration's GT-3 flight.
Source: NASA photo in my possession