He learned about Spanish folk tales and ballads from his uncle, Don Ramon Martinez, who lived in the mountains of southern Colorado.
The family then moved to Boulder, Colorado, so Espinosa and his older brother, Tobias, could attend college there.
He became a lifelong friend and colleague of Ramón Menéndez Pidal, to whom he presented 200 versions of forty uncollected ballads in Spain (similar to what his son would do later before the Spanish civil war).
[4] He was also amongst the founders of the Societe Internationale de Dialectologie Romane in 1909, the American Association of Teachers of Spanish in 1917 (later president in 1928), and the Linguistic Society of America in 1925.
[3] Espinosa was one of the first academic folklorists who took interest in using American materials, creating a precise methodology and framework to folklore studies.
He started his examination and analysis of the Spanish language more than fifty years after the U.S.-Mexico War and the subsequent occupation of New Mexico by Anglo-Americans, which means he came to study a cultural identity that was disrupted and often contested.
He began with his dissertation, Studies in New-Mexican Spanish (1909), which was published in three parts (Phonology, Morphology, the English Elements) between the years 1909 and 1914.
[citation needed] He did extensive research with Franz Boas on the influence of Spanish on the Pueblo Indians, natives of the New Mexico region.