McDonald's adopted the first version of its Golden Arches logo in the 1960s. The symbol developed from the large yellow arches used in the architecture of restaurants built during the previous decade.
The early arches were practical visual devices: they helped restaurants stand out to passing motorists. As McDonald's expanded, the company recognized that the paired curves could identify the business even without the full restaurant building.
In 1962, Jim Schindler created a logo that combined the arches into an “M” shape. The design was later refined, but the 1960s were the crucial decade when the architectural idea became a formal corporate mark.
The timing is sometimes placed in the 1950s because that is when the arches first appeared on restaurant buildings. The question concerns adoption as a logo, not the earlier architectural installations.