He is a scholar, lawyer, historian, journalist jurist, philosopher, bibliophile, biographer, philologist, painter, poet, musician, literary critic, politician, librarian, translator, linguist, researcher, philanthropist, and a Filipino genius.
He is considered great among Filipino Scholars. EDSA, the longest and foremost street of the Philippines and the most popular Philippine road was named after him.
As a writer, De Los Santos is considered one of the leading Filipino writers of the Spanish language of his time. He was the first Filipino to be elected a member of the Royal Academy of Language, the Royal Academy of Literature, and the Royal Academy of History of Spain in Madrid.
He was co-editor of the revolutionary newspaper La Independencia, and co-founder of the newspapers La Libertad, El Renaciemento, La Democracia, La Patria, and Malaysia.
He has published articles on Philippine history and culture, Algo de Prosa (1909), Literature Recorder (1911), El Teatro Tagalo (1911), Nuestra literature a traves del century (1913), El Proceso del Dr. José Rizal (1914), Folklore Musical de Filipinas (1920), Filipinos and filipinistas, Filipinas for Filipinos, Cuentos and paisajes Filipinos, and Criminality in the Philippines (1903–1908).
He is a native speaker of Spanish, English, French, German, and Tagalog.
As a scholar, he contributed to the first studies in the Philippines of anthropology, ethnology, archeology, linguistics, and demography. He traveled to European museums and libraries to gather rare documents and materials about the Philippines.
As a statesman, De los Santos was elected governor of Nueva Ecija in 1902 and 1904. He was the first governor of the province to be democratically elected. After his term, he was appointed the provincial prosecutor of Bulacan and Bataan. In 1925, Governor-General Leonard Wood appointed him director of the National Library and Museum.
He was born on 7 April 1871 in Malabon to parents Escolastico de Los Santos of Nueva Ecija and musician Antonina Cristobal of Malabon. He obtained from the Ateneo Municipal de Manila a Bachelor of Arts degree with the honor of summa cum laude and then took up a law degree at the University of Santo Tomas. He took the bar examination and landed first place. He had four children by first wife Ursula Paez and eight children by second wife Margarita Torralba.