[5] After several years working as an army contractor in Brooklyn, where he reputedly met Captain Robert E. Lee, Jack read about the 1848 finding of gold in the Sierra Nevada.

In November of that year he sailed with an artillery regiment to California, arriving in San Francisco in April 1849.

Having invested in revolvers Jacks made a $4,000 profit upon landing in San Francisco, and then took up a job at the city's Customs House.

[5] In 1850, Jacks moved to Monterey, California initially taking up a job in the store of a fellow Scotsman, James McKinlay.

By 1852 Jack had been elected Treasurer of Monterey County, California and began purchasing land in the area.

[5] Jacks soon involved himself in the settlement of Mexican land claims in the new State of California, a process that would lead to his becoming Monterey's dominant landowner.

The author Robert Louis Stevenson, after visiting Monterey, claimed that famed San Francisco orator Denis Kearney had suggested the residents should deal with Jack by having him hanged.

In 1875, he donated land on the Monterey Peninsula to a Methodist retreat group, which founded the town of Pacific Grove, California.

A dairy Jack owned along the Salinas River produced a cheese originally known as Queso Blanco, first made by the Franciscan friars at the nearby Mission San Carlos Borromeo de Carmelo.

There are also claims that "Monterey Jack" cheese originated from the Victorine Ranch, south of Malpaso Creek in Carmel Highlands.

[9] David Jacks married Maria Christina Soledad Romie (1837-1917) on April 20, 1861, in San Luis Obispo, California and produced nine children, with only seven surviving childhood.

[12] A devout Presbyterian, Jacks donated a great deal of money to religious causes later in life, including support of missionary work, as well as helping to found the Pacific Grove retreat.

He was on the board of trustees of the University of the Pacific and helped to keep the school financially afloat in its early years.

The gift to Stanford University was the largest at the time since the founding grant, with two endowed professorships and a building in the main quad named for the family.