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. He started cutting up large tracts of land south of Salinas into ranches for farmers to buy or rent. Jacks's business practices created a great deal of antipathy in the community. Jacks was a willing lender of money and of
mortgages to those living on his land, but also was quick to
foreclose. As a result, animosity toward him ran high, and it has been claimed he had to travel with
bodyguards anywhere he went in Monterey County. 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 June 1874, Henry Cerruti, in the employ of
Hubert Howe Bancroft, interviewed Dorotea Valdez, whose father was Juan Bautista Valdez, a member of the
Portola expedition. Dorotea lived in a pueblo, which she asserted was illegally obtained by Jacks. When Cerutti asked her if she knew him, this is what she said:Jack was also involved in land development. In 1875, he donated land on the Monterey Peninsula to a
Methodist retreat group, which founded the town of
Pacific Grove, California. In 1874 he helped found the Monterey and Salinas Railroad to compete with the dominant
Southern Pacific Railroad, though Jack eventually had to sell the line to the SP. There are competing claims to the origin of the name "Monterey Jack" cheese, including one by Domingo Pedrazzi of
Carmel Valley, who argued that his use of a pressure jack gave the cheese its name. There are also claims that "Monterey Jack" cheese originated from the Victorine Ranch, south of
Malpaso Creek in
Carmel Highlands. ==Personal life and death==