Coming from a modest family but being a brilliant student, he entered the municipal services in his hometown aged 20 years in 1860 with the vision of a grand boulevard that would allow urban sprawl outside the ramparts of Lille.
The mayor of Lille at the time, Augustus Richebé refused to support the project.
With Arthur Stoclet he pioneered a great project: the breakthrough Grand Boulevard between Lille, Roubaix and Tourcoing.
Alfred Mongy is one of the founders in 1900 of the Tramways Company and Northern Railways, which implements the construction of the Grand Boulevard Lille-Roubaix-Tourcoing.
Many changes have been made but two lines of Mongy still exist now with some updates to critical underground passages.