Subsequently, Muñoz Rivera was a member of a group organized by the party to discuss proposals of autonomy with Práxedes Mateo Sagasta, who would grant Puerto Rico an autonomous government following his election.

On August 13, 1898, the Treaty of Paris transferred possession of Puerto Rico from Spain to the United States and a military government was established.

In 1909, he was elected as Resident Commissioner of Puerto Rico and participated in the creation of the Jones-Shafroth Act, proposing amendments before its final approval.

His Paternal Grandfather Luis Muñoz Iglesias was from Castile in central Spain who decided to make his career in the army and received several recognitions after participating against Simón Bolívar during the Admirable Campaign, and followed his commanding officer Miguel de la Torre to Puerto Rico.

By the age of fourteen, Muñoz Rivera was managing legal documents, working with the local church clergy, and helping in his father's store.

Braschi advised Muñoz Rivera to continue writing, urging him to concentrate on science and politics, instead of authoring love poems.

[12] Muñoz Rivera then began writing about Puerto Rico's political status, promoting the necessity of an autonomous government.

[14] Other poems published by Muñoz Rivera were: Retamas, Tropicales, Horas de Fiebre, El paso del déspota, Minha terra, Cuba rebelde, A cualquier compatriota, Las campanas, Turba multa, Alea jacta est, Judas, El general, Abismos, Patriota, Himno, Parias and Poemas Liricos.

[15] The Autonomist Party's base grew rapidly, in part due to Muñoz Rivera's writings and speeches directed toward the jíbaro population.

[16] The Conservative Party considered this a threat and closed the newspapers where he published his work, sending part of their staff to jail in Fort San Felipe del Morro.

[16] After Francisco Cepeda Taborcias, editor of La Revista de Puerto Rico's was jailed, the position was offered to Muñoz Rivera, who accepted it.

He subsequently noticed that his travel had caused controversy within the Autonomist Party, which became divided between followers of Barbosa and Muñoz Rivera, with the two factions becoming known as Muñocistas and Barbosistas.

[23] Sagasta proposed that if he won the premiership of Spain, Puerto Rico would receive a Chapter of Autonomy which would give it the same degree of sovereignty that the Spanish provinces had.

Sagasta became Spain's prime minister following the power vacuum that occurred after the assassination of Antonio Cánovas del Castillo, and in December 1897 he granted the promised autonomous government.

[25] He had just learned that the American vessel USS Maine had sunk off the coast of Cuba, which would most likely spark a war between Spain and the United States.

However, Muñoz Rivera was saddened by the news, knowing that the United States was planning to build a canal in Panama, and that Puerto Rico would be a strategic location to protect the structure.

As part of this amnesty, Spain ceded Cuba and Puerto Rico, converting the archipelago into a possession of the United States under military governorship.

[27] He refused to cooperate with the military government and returned to Barranquitas, where he wrote a poem titled Sísifo, comparing Puerto Rico's political situation to Sisyphus' punishment.

[31] Henry eventually dissolved the Cabinet, removing the final remnants of recognition of the autonomous government established under Spanish rule.

Later that year, he founded the newspaper El Territorio, which voiced the concerns of landowners that were being affected by a blockade imposed by the United States.

[33] The Foraker act failed to prevent the monopolization of land, and allowed four American corporations to control of most of Puerto Rico's agricultural terrains.

One day while working for an article in El Diario, a friend of Muñoz Rivera brought a newspaper informing that all education in Puerto Rican public schools would be taught in English.

Muñoz Rivera began publishing articles directed towards the jíbaro population, in which he promoted self-government for Puerto Rico.

After receiving further threats from the statehood movements, Muñoz Rivera decided to move to New York City, not before leaving the paper's editing in charge of one of his followers.

[38] Muñoz Rivera, together with Rosendo Matienzo Cintrón, Antonio R. Barceló, José de Diego and Juan Vías Ochoteco founded the Union of Puerto Rico party, which won the election in 1904.

On March 2, 1917, the Jones-Shafroth Act was signed, granting United States citizenship to Puerto Ricans and creating a bicameral Legislative Assembly.

[42] In late 1916, Eduardo Georgetti, a friend of the family, summoned his wife and son to Puerto Rico and informed them that he was suffering from an infection that had begun in the galbladder, before expanding throughout his body.

[43] Luis Muñoz Rivera died on November 15, 1916, in the town of San Juan, before the Jones Act was enacted into law.