What kind of background information did the author need to find out to be able to write this book ?

Nazario was inspired to write Enrique’s Journey after discovering that her friend and maid, Carmen, had left her four children behind in Guatemala so that she could earn money in the U.S. to support them. When Carmen's son Minor later arrived, having braved a journey fraught with dangers, he told Nazario about El Tren de la Muerte (The Train of Death) that migrants must brave to make it to the U.S.

Nazario soon discovered that Carmen and Minor’s story was not uncommon among the immigrants who arrive in the United States illegally from Central America and Mexico each year. In fact, she realized, it was particularly common for single mothers and their children.