If the family was eating their garden (instead of selling it for money to buy food) it wouldn't need to be even an acre, Janie. My friend canned enough greenbeans from two rows (appx 15ft long) in one season to last two years with frequent eating.
A row of tomatoes gave her plenty to can as juice and salsa with enough beyond that to foist off on everybody who was interested in having some.

It's not the size of the garden, you know...it's how you use it.