Seventy years ago, the McGill University 100-MeV synchro-cyclotron was under construction. During its almost 40 years of operations, many discoveries were made and a large number of doctoral students were educated. The long-term influence of the cyclotron lab on the landscape of Canadian subatomic physics was considerable and is arguably greater than that of Rutherford, an earlier engine of discovery at McGill.
The cyclotron owed its existence to the vision of John Stuart Foster who almost single-handedly led its funding and building stages, using his considerable scientific prestige and personal skills as well as his important connections in the international community. In this presentation I will describe the path he took, starting with his initial proposal, made in 1935, only three years after Lawrence and Livingston's first demonstration of the cyclotron concept.