The earliest article about Africans accompanying the Spanish expeditions in the Americas during the sixteenth century can be read by clicking HERE.
It was written by Richard R. Wright Sr., a former slave who became the highest-ranking American officer as a major in the Spanish-American War. There are a few historical miscues in the article because it was published in 1902 in the magazine American Anthropologist before some events were clarified by later researchers. Nevertheless, it's the best single article ever written about the mostly ignored involvement and contributions of Africans in the 1500s from the southern U.S. through Mexico and into Central America and South America.
Although the "Black Conquistador" Juan Garrido is not mentioned, Esteban is the main point of discussion in most of the article.