The large radio telescope (Le Grand Radiotélescope) at the Nançay radio astronomy field station of Paris Observatory was built between 1958 and 1966 on the model of the Ohio State University radio telescope, with which a large collecting area was obtained at low cost. The Nançay radio telescope, with a surface area of 7,OOO m², is a meridian instrument which can observe equatorial sources for 30 minutes on each side of the meridian transit of the source. We describe the origin and the construction of this instrument. We also describe the evolution of the focal systems and give an outline of the first spectral and continuum observations obtained with the radio telescope in the wavelength range 6 to 32 cm.