The principal portions of San Marino were included in a Mexican Land Grant in 1830 to an Indian lady named Senora Victoria Reid, the widow of an Englishman. She named her Rancho, Huerta de Cuati. Prior to this grant , the area was part of the San Gabriel Mission (the "Old Mill" was the grist mill for the Mission), and before that was occupied by the Gabrielino Indians with their village located at what is now Huntington School.

In 1852, Mrs. Reid deeded her Rancho to Don Benito Wilson. Later, Wilson deeded the main portion to J. de Barth Shorb, who named his Rancho after his grandfather's plantation in Maryland, which in turn had received its name from the Republic of San Marino, in Italy.

The San Marino Republic was named after a Dalmatian stone-cutter, by the name of Marino, who fled nearly sixteen hundred years ago from his home on the Dalmatian coast at the time of a Turkish invasion, and took refuge among the rocky crags of Monte Titano, which commanded a view of the Adriatic Sea. In 1085 A.D., the Monastery at Mt. Titano canonized Marino and changed his name to San, which means Saint, hence Saint or San Marino.

In 1903, the Shorb Estate was purchased by Henry E. Huntington and in 1913 the three primary Ranchos of Wilson, Patton, and Huntington, together with the subdivided areas from those and smaller Ranchos, such as Stoneman, White, Rose and others, were incorporated as the city of San Marino.

The first mayor was general George S. Patton, Sr.

The San Marino Seal contains the three summits of Mt. Titano, upon each of which reposes a tower, fortified with walls built from native rock and capped with a bronze plume, all surrounded by a heart-shaped scroll with two roundels and a lozenge (of unknown significance) at the top. Underneath the left side is a graceful palm frond and underneath the right side, a branch from an orange tree. The crown representing the monarchy on the original was removed when the City’s Coat of Arms was redesigned by William Hertrich in the 1920s.

The first San Marino school was opened at the corner of Monterey Road, (then called Calle de Lopez) and Oak Knoll, in what was known as the Old Mayberry Home, on September 9, 1917, with three teachers and thirty-five pupils, grades kindergarten through the eighth. Our High School students attended South Pasadena High until San Marino High School graduated its first class in 1956. Our High School nickname, "The Titans," comes from Mt. Titano, in the Republic of San Marino.