The origins of the Mini Cooper can be traced to the development of the original Mini by BMC and designer Sir Alex Issigonis in the 1950s. Responding to a fuel shortage, and the need for more efficient city cars, the Mini was developed as a two door, 4 cylinder engine car by BMC, and featured a monocoque shell. The first Mini, or Mark I, was tied to BMC’s other brand names, which included the Morris Minor and Austin, and was launched in 1959. During the 1960s, the popularity of the compact Mini led to it taking on its own distinctive identity, with the Mark II Mini adding a new grille in the later part of the decade.
Source: BMW Blog