Wikipedia Article About Jack cheese on Wikipedia Monterey Jack is a type of semi-hard cheese using pasteurised cows’ milk. It is commonly sold by itself, or mixed with Colby cheese to make a marbled cheese known as Colby-Jack (or Co-Jack). One story of the origin of the name is that it was first made in the town of Monterey, California by a large land-owning family named the Jacks. They produced a mild, white cheese at their ranch, which came to be known at first as "Jack's Cheese", and eventually "Monterey Jack".