Rotterdam in the 17th and 18th centuries was a principal port of departure for transmigrants to America. Typically they came from the Rhineland and their goal often was Pennsylvania, the colony that was founded on 4 March 1681. It is difficult to identify the specific reasons for the Rhinelanders going to America. The migration flow was erratic. Economic pull was only a partial explanation. Richard W. Unger examines all factors, both push and pull, in 'Income differential, institutions and religion: working in the Rhineland or Pennsylvania in the 18th century'(in Working on Labor, 2012, pp 269-295). Unger stresses the crucial role of British and Dutch merchants based in Rotterdam, in the transport business of transmigrants. They were often migrants themselves. The work and involvement of these merchants largely determined the volume, direction and business cycle of German workers who wanted to settle in North America.