After reaching record high levels during the spring and summer of 2014, the flow of Central American unaccompanied children (UACs) and families arriving at the U.S.-Mexico border declined sharply. Data from U.S. Customs and Border Protection (CBP) show a resurgence in the numbers of child migrants and families from El Salvador, Guatemala, and Honduras arriving in the United States in the summer and fall of 2015. What caused the sharp drop in Central American child and family migration flows in summer 2014, and why have the numbers begun to climb once again? Undoubtedly, numerous factors contributed to the downturn. The United States intensified its enforcement efforts at the U.S.-Mexico border, detained large numbers of Central American women and children, targeted more resources to investigate and prosecute migrant smugglers, and worked with the Northern Triangle countries on a public information campaign to discourage outflows. Perhaps most importantly, Mexico significantly stepped up its enforcement, with the advent of the Southern Border Program. Guatemala and Honduras also took additional steps to secure their common borders and Guatemala's border with Mexico; and the three Northern Triangle countries announced a large-scale development strategy known as the Plan for the Alliance for Prosperity. While the drop in child migration and family arrivals in 2014 led some to believe the regional migration crisis had been resolved, rising flows in 2015 offer a reminder that humanitarian and migration pressures in the Northern Triangle remain a major concern, and that smuggling networks play a significant role. This fact sheet examines influencing factors on the recent trends in unaccompanied child and family arrivals from Central America to the U.S.-Mexico border, as well as Mexico's role in enforcement.