He graduated "magna cum laude" with a degree in Business Administration in 1979. In Puerto Rico, he met Milagros, the woman that would become his wife. They married in 1971 and had three children together. In 1990, Santiago moved to Phoenix, Arizona, with his wife and children. At this point he reflected, "the only role models and heroes for Latino children were El Zorro, the Cisco Kid and Speedy Gonzales and," he said, "school textbooks failed to mention the many contributions that Latinos had made to the formation of our country [the United States]." In response, Santiago began publishing a series of short articles about the contributions that Puerto Ricans had made to the American society. He is the editor of the Puerto Rican Military History Channel of the monthly internet magazine "El Boricua", a staff writer in the internet magazine "Somos Primos" and the official historian of the Association of Naval Services Officers (ANSO). His early published work focused on military history, but later he expanded his research and documentation to include many other facets of the Puerto Rican life experience. One email received from a reader of his articles led to Santiago serving to bridge two families that had lost track of each other for many years. It happened in 2007, when Santiago united U.S. Army veteran William W. Kouts with the family of the late David M. Gonzalez. Gonzalez had sacrificed his life to save Kouts during World War II. On April 2010, Santiago discovered and wrote about Lt. Augusto Rodriguez a Puerto Rican who served in the American Civil War. It was the first time that a link in the American Civil War was made between Puerto Rico and the United States. Rodriguez was thus the first known Puerto Rican veteran of the United States Armed Forces. The significance of this discovery is that, until then, it was believed that Puerto Ricans had not served in the United States military prior to World War I. Puerto Rico's Secretary of State, Kenneth D. McClintock, named Santiago "Puerto Rico's foremost military historian." Santiago is among the people who were interviewed and who are featured in the documentary ""; directed and produced by Los Angeles-based filmmaker Mylene Moreno. The documentary, which aired on PBS in September 22, 2015, examines the Latino experience during the Vietnam War. He was interviewed, together with fellow veteran Oscar Urrea, by PBS "Horizante" host Jose Cardenas and Univision newscaster Jorge Valenzuela, where he expressed his personal experiences, prior to the showing of the documentary.