Towards the end of the First Industrial Revolution, the area saw rapid growth in population and urban development. This expansion was in part due to an influx of working class laborers and immigrants looking for factory jobs and dock work, as well as the first wave of mass immigration of Irish refugees or impoverished immigrants from Ireland in the wake of the Great Irish Hunger. South Philadelphia's urbanized border eventually expanded to reach that of Philadelphia proper, or what is today known as Center City Philadelphia. Along with all other jurisdictions in Philadelphia County, South Philadelphia became part of the City of Philadelphia proper with passage by the Pennsylvania legislature of the city–county Act of Consolidation, 1854.