No evidence of human habitation on Socorro exists before its discovery by Spanish explorers.
Hernando de Grijalva and his crew discovered an uninhabited island on 19 December 1533, and named it Santo Tomás (Socorro Island) and on 28 December they discovered Isla de los Inocentes (San Benedicto) which owed its name to having been found on the day of the Holy Innocents.

In November 1542, Ruy López de Villalobos, while exploring new routes across the Pacific, rediscovered Inocentes and Santo Tomás and charted the latter as Anublada ("Cloudy").
Villalobos was the first to report sighting of Roca Partida Island giving it its present-day name.
In 1608, Martín Yánez de Armida, in charge of another expedition, visited Anublada and changed its name to Socorro.
In 1779 José Camacho was the first to report sighting of the island remaining, that he charted as Santa Rosa ("Saint Rose").
Santa Rosa was later renamed Clarion after the vessel commanded by Henry Gyzelaar at that time.

The Revillagigedo Islands have been visited by a number of other explorers: Domingo del Castillo (1541), Miguel Pinto (1772), Alexander von Humboldt (1811), Benjamin Morrell (1825), Sir Edward Belcher (1839) who made the first botanical collections and Reeve, who witnessed the eruption of Mount Evermann in 1848.
On 25 July 1861, President Benito Juárez signed a decree awarding territorial control over the four islands to the state of Colima.
His plan was to build an offshore penitentiary on Isla Socorro; although this never happened, the decree whereby they were attached to Colima has never been repealed.
In 1865, the island was explored by ornithologist Andrew Jackson Grayson, who discovered the Socorro dove, Socorro mockingbird and the Socorro elf owl which were later given scientific names in his honor.
No evidence of human habitation on Socorro exists before its discovery by Spanish explorers. Hernando de Grijalva and his crew discovered an uninhabited island on 19 December 1533, and named it Santo Tomás (Socorro Island) and on 28 December they discovered Isla de los Inocentes (San Benedicto) which owed its name to having been found on the day of the Holy Innocents.
In November 1542, Ruy López de Villalobos, while exploring new routes across the Pacific, rediscovered Inocentes and Santo Tomás and charted the latter as Anublada ("Cloudy"). Villalobos was the first to report sighting of Roca Partida Island giving it its present-day name. In 1608, Martín Yánez de Armida, in charge of another expedition, visited Anublada and changed its name to Socorro. In 1779 José Camacho was the first to report sighting of the island remaining, that he charted as Santa Rosa ("Saint Rose"). Santa Rosa was later renamed Clarion after the vessel commanded by Henry Gyzelaar at that time.
The Revillagigedo Islands have been visited by a number of other explorers: Domingo del Castillo (1541), Miguel Pinto (1772), Alexander von Humboldt (1811), Benjamin Morrell (1825), Sir Edward Belcher (1839) who made the first botanical collections and Reeve, who witnessed the eruption of Mount Evermann in 1848. On 25 July 1861, President Benito Juárez signed a decree awarding territorial control over the four islands to the state of Colima. His plan was to build an offshore penitentiary on Isla Socorro; although this never happened, the decree whereby they were attached to Colima has never been repealed. In 1865, the island was explored by ornithologist Andrew Jackson Grayson, who discovered the Socorro dove, Socorro mockingbird and the Socorro elf owl which were later given scientific names in his honor.
Revillagigedo Islands