On Sept. 14, 1966, NASA's Gemini 11 mission set an all-time spaceflight altitude record when two astronauts reached an orbit of 850 miles above the Earth.

This remains the highest altitude ever achieved by a crewed, non-lunar mission. Gemini 11 command pilot Pete Conrad and pilot Dick Gordon spent three days orbiting the Earth in their cramped Gemini spacecraft. After launch, they performed the first-ever direct-ascent rendezvous with an Agena target vehicle.
Once the two spacecraft were adjoined, they used the rocket on the Agena target vehicle to ascend to their record-breaking altitude. They also created a little bit of artificial gravity while in orbit by using their thrusters to rotate the combined spacecraft.