Posted to the island of Cuba in 1850, he was interim commander general of the Eastern Department of the island until 1855 and, from that date, civil governor in said department, where he served until 1860, deserving the Grand Cross of San Hermenegildo. During his ten years in Santiago de Cuba he was known as "the builder" and would later come to be considered the best colonial governor that the Eastern Department had had due to the public works he carried out: he ordered the first sidewalks to be laid in the city of Santiago, the construction of hospitals, cemeteries, barracks and the first commuter trains. According to Luis Mauricio, at the inauguration of the Príncipe Alfonso Hospital, Vargas organized military maneuvers between Santiago de Cuba and El Caney, since he thought that the Americans would take over Cuba through Guantanamo. Today, in Santiago de Cuba, there is still a Vargas street named after him. The Cabo Cruz lighthouse, built during his government, is still known today as the Vargas lighthouse. In 1861 he was assigned as second corporal to Puerto Rico, on commission, becoming dependent on the expeditionary division that was being formed against Mexico. Carlos de Vargas would be named second land chief, under the orders of General Prim . After the Spanish and French troops took Veracruz, Vargas was named governor until April 1862, when Prim broke the Treaty of London and ordered the return of the Spanish troops. On May 21, 1862, Vargas was assigned to the Santo Domingo campaign as second in command of the Spanish military expedition. He participated in the actions of Sabaneta, Santiago de los Caballeros, Montecristi, Cibao, Puerto Plata and Altamira, obtaining in 1862 the sash of field marshal and the Grand Cross of Charles III.That same year, he was named Gentleman of the Chamber of His Majesty.In 1863, he was named captain general of Santo Domingo. In the
Dominican Restoration War, he was successful in reconquering the province of Azúa for Spain and defeating the Dominican insurgents in San Cristóbal, Doñana, Pulgarín, Sabana-Buey and Azúa. In 1864, Vargas ceased to be in command of Santo Domingo. The following year, in 1865, the Spanish troops were defeated and evacuated the island. ==Later years and death==