Toponymy
The origin of the name for the river is somewhat ambiguous. It did not, however, receive its name during the Spanish or the Mexican eras. It was first encountered by the Spanish Portola Expedition on September 27, 1769, and so was named for the saint celebrated on that day, San Elizario. However, it subsequently appeared on many maps as the Rio de Monterey and its valley was called the Valle de Monterey. It was called Rio de Monterey by Fr. Pedro Font on March 4, 1776 and the Monterey River as late as 1850. It first appears on an American map in 1858 as the Rio Salinas, perhaps because of the large salt flats noted near its mouth in that era.
Read more about this topic: Salinas River (California)