The first land grands were made in Rosarito in the year 1827. And after secularization of the mission lands in 1833, it has been estimated that over 700 private land grants were made in California within the nest decade.

Baja California had its share, with many of the grantees being families who were prominent in Alta California. One of the largest in the northwestern sector was Rancho El Rosario, or Rosarito. It extended from what is now the southern edge of the San Antonio Shores development to the Rosarito River bounded on the west by the ocean and stretching eastward to the peaks of the mountains. The first grant had been made to Don Jose Manuel Machado in 1827 by the Mexican governor, Jose Maria Echeandia Machado had been born in San Gabriel and had grown up and married in San Diego. His land grants, along with the later one of the famous ranchos that marked the "age of the Dons". It may be said that it was at this time that the people of Rosarito first learned to party.

"The Age of the Dons", the Golden Age, is probably best remember for the hospitality and sociability of the people on barbecues were the order of the day. All classes of society and all people from surrounding rancho took part, and though the music was a far cry from the heart of native musicians and the vigorous stamp of dancer's feet.
Great herds of cattle and horses roamed the brown hills, and it was at this time that the Rosaritans first became renowned for their fine mounts. Truly the vaqueros who bring their horses to the beach for tourist to ride and to splash through the surf are part of those great traditions of the past.

It was at this time also that there was a migration of people from Western Europe to the ranchos of Baja. Names like Ames, Crosthwaite, Gilbert, and Ireland, joined the Machados, Yorba's, and Valdez's on the ranches of the time. Intermarriage was common, and the cultures blended then as they do today, resulting in families with names Machado Gilbert, Crosthwaite Machado, Yorba Gilbert, Ames Crosthwaite, etc. even to this day.