Louis Andrew (L.A.) Murillo was born in 1922 in Southern California to Filomeno and Refugio (Ruth) Murillo. His parents moved to the United States in 1916 from Michoacan, Mexico, escaping from the Mexican Revolution. Murillo grew up in Pasadena, California, where he attended public schools. He enlisted in the Army Air Force in 1942, and served through the end of the war as part of a bomber crew in the 15th Air Force, Italy. Upon his discharge in 1945, he enrolled at the University of Southern California. He graduated with his BA in 1947 and completed a MA in Spanish Literature, also at USC, in 1949. As a student at USC he traveled and studied in Spain with assistance from a Del Amo Foundation grant.
After graduating from USC, Murillo earned a Ph.D. in Romance Languages and Literature from Harvard University in 1953 and taught there until 1957. In 1958, Murillo moved to the University of California, Berkeley, where he taught Spanish literature and became a Cervantes scholar. He retired as a Professor Emeritus in 1986. After retiring, Murillo moved back to Southern California. In 1985 he donated his important scholarly book collection on the works of Miguel de Cervantes Saavedra to the USC Libraries new Boeckmann Center for Iberian and Latin American studies. He also employed his knowledge of Spanish in his volunteer work for the Los Angeles Police Department and the California Highway Patrol. He assisted the agencies as a bilingual consultant, producing Spanish language field guides and taking phone reports in either English or Spanish. While volunteering, he also collected pamphlets, notices and flyers in English and Spanish to help with the compilation of his guides and dictionaries and to document Spanish language usage in Southern California after 1975.