Andrew Cassidy was a native of County Cavan, Ireland. He came to America when 17 and was employed three years at West Point, in the Engineering Corps, under General George B. McClellan. He then went to Washington and entered the employ of the Coast Survey Office, under Professor Bache. About a year later, he was one of a party sent to the Pacific Coast under Lieutenant W. T. Trowbridge. They reached San Francisco in July, 1853, and a month later came to San Diego, established a tidal gauge at La Playa, and left Cassidy in charge. He remained in charge of this tidal gauge, and of meteorological observations, for seventeen years, and also gave considerable attention to collecting specimens for the Smithsonian Institution.
In 1864, Mr. Cassidy became owner of the Soledad Rancho, containing 1,000 acres, where the town of Sorrento is situated, and engaged in the live stock business until in 1887, when he sold the property. He is also a property owner in San Diego.
His first wife was Rosa Serrano, daughter of José Antonio Serrano, who died September 10, 1869. He married, second, Mary Smith, daughter of Albert B. Smith, who is now deceased. They had one daughter, Mary Winifred. Mr. Cassidy is still living, a respected citizen of San Diego. He held several public offices at an early day. He was a member of the Board of Public Works as late as his 88th year.
[from William Ellsworth Smythe's History of San Diego, pages 267-268]