He was born in sitio Cupang, barrio San Nicolas, Bulacan on August 30, 1850 to Don Julian Hilario and Blasa Gatmaytan. He added the surname del Pilar pursuant to the 1849 Claveria decree.

He earned his Bachelor of Arts degree at the Colegio de San Jose and at the University of Santo Tomas, he pursued law but he was suspended before graduation due to an altercation with a priest in San Miguel over an increase of baptismal fees. He worked as oficial de mesa in Pampanga and finally obtained his licentiate in jurisprudence in 1889.

Though he was active in discussions with his friends who favored change through education like Marciano Ponce, Numeriano Adriano and Apolinario Mabini, he escaped prosecution in 1872. After finishing law, he worked for the Manila Royal Audiencia and at the same time he spread nationalist and anti friar ideas in Manila and in towns and barrios of Bulacan. His fluency in Tagalog effectively disseminated his convictions through the duplohan, dalit and oration in whatever venue-fiestas, cockpits, and even baptismal parties. In 1882, he co-founded the Diariong Tagalog, a bilingual paper. In this paper, nationalist and reformist articles were published. He also organized various anti-friar demonstrations with petitions for the expulsion of friars from the Philippines. He organized the Junta de Programa which functioned to collect funds to carry the propaganda work, to disseminate propaganda materials and constitute liason between the propagandists in Spain and Philippines. He produced propaganda materials in the form of a series of pamphlets assailing the friars in the country entitled Kai-ingat Kayo (a defense of the Noli Me Tangere of Jose Rizal which was under the attack of Fray Jose Rodriguez), the Dasalan at Toksohan (a kind of prayer book mocking the cathecism and other prayers) and the Pasiong Dapat Ipag-alab nang Puso Nang Taong Babasa (an intense attack on the friars). Due to these activities, he was hounded by friars and Spanish officials. He secretly left the Philippines for Spain on October 28, 1888.

On his way to Spain, he wrote Sagot nang Espaņa sa Hibik nang Filipinas and the Kadakilaan nang Dios. In Spain he wrote the La Soberania Monacal en Filipinas (a detailed indictment of the predominance of the friars in Philippine life). Upon reaching Barcelona, he joined the Filipino propagandists and founded a paper, La Solidaridad. The paper advocated a policy of assimilation of the Philippines as a province of Spain. He succeeded Graciano Lopez Jaena as its editor, he contributed numerous articles and used different pen names such as Dolores Manapat, Piping Dilat, Siling Labuyo, Kupang, Haitalaga, Patos, Carmelo D.A. Murgas, L.O. Crame and Plaridel.

Funding for the La Solidaridad became scarce and eventually stopped, his health failing due to work, sleepless nights and hunger, he died in Barcelona on July 4, 1896 of tuberculosis.