On June 3, 1965, astronaut Ed White climbed out of Gemini 4, becoming the first American to perform a spacewalk. It was just past 3:45 p.m. Eastern Daylight Time. He was attached to an 8-meter tether, and maneuvered using a handheld gun that spat compressed oxygen (it ran out of propellant after just 3 minutes, after which he just yanked on the tether to move around).
The spacewalk lasted 23 minutes, but it was a huge breakthrough for NASA. White and Command Pilot Jim McDivitt had some trouble opening the hatch at first, but they managed it eventually. The pair discovered that their communications system was a bit flaky; for the duration of the spacewalk, White couldn't hear CAPCOM (though they could hear him), relying on McDivitt to relay messages. Comically, McDivitt managed to put his own system in a mode where he couldn't hear CAPCOM either, and busied himself taking photos and movies while White was having the time of his life.
CAPCOM became increasingly frustrated, repeatedly trying to raise the astronauts in order to remind them of the 20-minute time limit, without a response. The timing was vital because CAPCOM would lose radio contact past a radio blackout point, and they wanted their astronauts safely in the spacecraft when that happened. Finally, McDivitt switched his communication system to a mode where he could hear the ground. This exchange speaks volumes:
McDivitt (speaking to White): I'm going out to PUSH-TO-TALK and see what the Flight Director has got to say. McDivitt: Gus, this is Jim. Got any message for us? Gus Grissom (CAPCOM): Gemini 4, get back in! McDivitt: Okay. ... McDivitt (to White): We're coming over the west now, and they want you to come back in now. White: Back in? McDivitt: Back in. Grissom (CAPCOM): Roger. We've been trying to talk to you for awhile here. White: Aw, Cape, let me just find a few pictures. Grissom (CAPCOM): No, back in. Come on. White: Coming in. Listen, you could almost not drag me in, but I'm coming. (Two minutes pass, with various chattering.) White: ...Actually, I'm trying to get a better picture. McDivitt: No, come on in. White: I'm trying to get a picture of the spacecraft now. McDivitt: Ed, come on in here! White: All right. Let me fold the camera and put the [maneuvering] gun up. (The better part of another minute passes, as they discuss where to stow the camera.) White: ...This is the saddest moment of my life. McDivitt: Well, you're going to find a sadder one when we have to come down from this whole thing.
He came in.
White was the second human to perform a spacewalk; he was preceded by cosmonaut Alexey Leonov, who made his walk just a few months earlier, on March 18, 1965. White was one of three astronauts who died in the tragic Apollo 1 fire in January 1967.
Here's a short film, narrated by White himself, about the spacewalk. (Sound starts around the 30-second mark.) It's wild seeing the actual film McDivitt took of the spacewalk. Behold: