Two days later, on Trinity Sunday, June 11, 1775,[5] Heceta, his men, and two Franciscan fathers who erected a cross on the summit claimed Trinidad Head for Spain in the name of King Charles III.

Over the next 75 years, Spanish, Russian and English ships landed at Trinidad Head to hunt sea otters, procure fresh water, and take refuge from storms.

[13] In January 2017, the United States Congress added the Bureau of Land Management's portion of Trinidad Head to the onshore area of the California Coastal National Monument.

[1] President Barack Obama used his executive power under the 1906 Antiquities Act to designate the Bureau of Land Management's portion as a unit of the National Monument.

[14] Trinidad Head is composed of metamorphosed gabbro embedded in the surrounding Franciscan melange, topped with Pleistocene sands and gravels.