Very interesting.

Vostok (Russian for ‘East’) was a Soviet human spaceflight project that developed the Vostok spacecraft which was used to place the first human in space.

The first manned US spacecraft was Mercury, which was first launched in suborbital flights on Redstone rockets and then in orbital missions on Atlas launchers.

The one-seat Vostok craft were replaced by Voskhod (in the Soviet Union), and two-seat Gemini replaced Mercury in the US.