The history of humans is a story of constant movement, beginning with early migrations out of Africa. Migrations can be explained through push factors, or why people leave a place, and pull factors, or why they go to a place. There are several economic, social, political, and environmental push and pull factors that we discuss in this review. Most migrants in the last several hundred years share characteristics defined by Ravenstein's Laws including short travel distance, settling in cities, and the demographics of migrants. We’ll also discuss the implications of colonialism on migrations and historical examples of forced migrations including diasporas, slavery, and natural disasters. Finally, we review the policies that have been used to encourage migrations and other anti-immigration policies meant to limit migrations.