Nauchno-Issledovatel'skii Ispytatel'nyi Poligon N.5 (NIIP-5),
or Scientific-Research Test Range N.5,
also known as the Tyuratam Missile Test Range (poligon in Russian)
and Cosmodrome Baikonur.
The Soviet government established the Nauchno-Issledovatel'skii Ispytatel'nyi Poligon N.5 (NIIIP-5), or Scientific-Research Test Range N.5 by its decree of 12 February 1955.
The U-2 high-altitude reconnaissance plane found and photographed for the first time the missile test range on 5 August 1957. The location of the new rocket center was identified on the map near the Bf., or Bahnhof (station in German), Tyuratam. Dino A. Brugioni, an assistant to the chief of the CIA's Photo-Interpretation Division (PID), named the launching site Tyuratam, following the intelligence community practice of naming installations after the nearby towns. The USSR kept the location of the missile range secret.
Only in 1961 after the launch of the first man to space, Yuri A. Gagarin, the Soviet Union publicly identified the launch site location as Baikonur after a small town ... nearly 200 miles (320 km) northeast away.
See M. Gruntman, Blazing the Trail, AIAA, 2004 for the historic and technological background and context.
Page 312 from Blazing the Trail shows fragments of the decree of the USSR Council of Ministers establishing the Tyuratam (Baikonur) Missile Test Range.
Page 321 from Blazing the Trail shows a composite satellite image of the early Tyuratam (Baikonur) launch complex, the cosmodrome, obtained by Corona on 30 May 1962. Also shown (zoomed in) are the first space launching pad (first satellite sputnik, first cosmonaut Gagarin) and the settlement, later called Leninsk.