The invention that played the biggest role in suburbanization was the automobile. It was not the only invention that played a role, and suburbanization was in progress even before cars were invented, but the car made suburbanization more widespread and more rapid.
Suburbanization depends on mobility. When suburbanization was beginning, suburbs were largely “bedroom communities” where people lived, but did not work. The people who lived in the suburbs had to be able to get to work in the cities. This means that inventions that allowed for greater mobility were central to suburbanization. Before cars were invented, there were “streetcar suburbs” that were accessed by streetcars. However, cars allowed for much more mobility than streetcars did. When cars were invented (and, more importantly, when they became common and when good roads were built to accommodate them), it became much easier for people to travel back and forth between cities and suburbs. Therefore, the invention of the car was central to the process of suburbanization.