A Bit of History
From Monterey County Historical Society, written by Teresa Russell a descendent of the Espinosa and Boronda families mentioned below.
"Article about Dona Boronda's Jack Cheese. She is (was) my grandmother.
The name "jack" is from the use of a vice she made the cheese with. My dad, Ralph Russell (now 76 years old) lived on Rancho Los Gatos, with his mother (Charlotte Espinosa) at Russell and Espinosa Roads in Castroville. The Espinosas and Borondas came to California on pack trains in the 1700s. Dona Boronda brought her cheese recipe with her and started a dairy operation. The "jack" was a "vice."
My dad tells about how the milk was poured down into this jack device, and as it turned to cheese, it was squeezed between wooden paddles of the vice/jack that fit in the box. The handles were pulled together and bound by leather straps to hold the cheese. The whole gizmo was called a jack, because it pressed the cheese.
The Borondas sold this cheese to a man named [David] Jacks, who had a store. Jacks also exported the cheese on ships out of Monterey. Jacks identified his crates by stamping them "Jack Cheese."
But the original method of using a jack to make the cheese came from Espinosa Spain. (The Boronda and Espinosa families both came from Spain).
Teresa Russell [y Espinosa de Boronda]
As you can see from the above article, there are several alternative explanations for how Monterrey Jack got its name. However, David Jacks is most often credited as the cheese’s namesake.
In 1882, David Jacks began shipping a cheese branded with his last name and the city of origin, Monterey, Calif. People would ask for “Jack's Monterey” and over time the “s” was dropped and people began asking for Monterey Jack.