"Botanically speaking, tomatoes are the fruit of a vine, just as are cucumbers, squashes, eggplants and peppers. But in the common language of the people ... all these are vegetables, which are grown in kitchen gardens, and which, whether eaten cooked or raw, are, like potatoes, carrots, parsnips, turnips, beets, cauliflower, cabbage, celery and lettuce, usually served at dinner in, with or after the soup, fish or meats which constitute the principal part of the repast, and not, like fruits generally, as dessert.
In 1893 , the Supreme Court ruled that the tomato must be considered a vegetable, even though, botanically, it is a fruit. Because vegetables and fruits were subject to different import duties, it was necessary to define it as one or the other. So, tomatoes were declared to be a vegetable given that it was commonly eaten as one."

(Source: The Packer, 6/9/90)